Description of problem:
When adding a RHV-4.3 to CFME-5.10, the initial refresh fail,
as well as consecutive provider refresh trials. 

In the provider summary page, this error appear, in the "Last Refresh" section: "Error - 18 Minutes Ago
undefined method `ems_ref' for nil:NilClass"

Version-Release number of selected component (if applicable):
RHV-4.3.1.1-0.1.el7
CFME-5.10.0.33


evm.log Error:
[----] E, [2019-02-26T08:49:16.509152 #19943:f2af58] ERROR -- : MIQ(ManageIQ::Providers::Redhat::InfraManager::Refresh::Strategies::Api4#refresh) EMS: [RHV], id: [2] Refresh failed
[----] E, [2019-02-26T08:49:16.511159 #19943:f2af58] ERROR -- : [NoMethodError]: undefined method `ems_ref' for nil:NilClass  Method:[block (2 levels) in <class:LogProxy>]
[----] E, [2019-02-26T08:49:16.511285 #19943:f2af58] ERROR -- : /opt/rh/cfme-gemset/bundler/gems/cfme-providers-ovirt-fe67891d889e/app/models/manageiq/providers/redhat/inventory/persister/definitions/infra_group/vms_dependency_collections.rb:63:in `block (2 levels) in ems_folder_children_custom_save_block'
/opt/rh/cfme-gemset/bundler/gems/cfme-providers-ovirt-fe67891d889e/app/models/manageiq/providers/redhat/inventory/persister/definitions/infra_group/vms_dependency_collections.rb:63:in `each'
/opt/rh/cfme-gemset/bundler/gems/cfme-providers-ovirt-fe67891d889e/app/models/manageiq/providers/redhat/inventory/persister/definitions/infra_group/vms_dependency_collections.rb:63:in `each_with_object'
/opt/rh/cfme-gemset/bundler/gems/cfme-providers-ovirt-fe67891d889e/app/models/manageiq/providers/redhat/inventory/persister/definitions/infra_group/vms_dependency_collections.rb:63:in `block in ems_folder_children_custom_save_block'
/opt/rh/cfme-gemset/gems/inventory_refresh-0.1.2/lib/inventory_refresh/save_collection/base.rb:22:in `save_inventory_object_inventory'
/opt/rh/cfme-gemset/gems/inventory_refresh-0.1.2/lib/inventory_refresh/save_collection/topological_sort.rb:29:in `block (2 levels) in save_collections'
/opt/rh/cfme-gemset/gems/inventory_refresh-0.1.2/lib/inventory_refresh/save_collection/topological_sort.rb:28:in `each'
/opt/rh/cfme-gemset/gems/inventory_refresh-0.1.2/lib/inventory_refresh/save_collection/topological_sort.rb:28:in `block in save_collections'
/opt/rh/cfme-gemset/gems/inventory_refresh-0.1.2/lib/inventory_refresh/save_collection/topological_sort.rb:26:in `each'
/opt/rh/cfme-gemset/gems/inventory_refresh-0.1.2/lib/inventory_refresh/save_collection/topological_sort.rb:26:in `each_with_index'
/opt/rh/cfme-gemset/gems/inventory_refresh-0.1.2/lib/inventory_refresh/save_collection/topological_sort.rb:26:in `save_collections'
/opt/rh/cfme-gemset/gems/inventory_refresh-0.1.2/lib/inventory_refresh/save_inventory.rb:24:in `save_inventory'
/var/www/miq/vmdb/app/models/ems_refresh/save_inventory.rb:5:in `save_ems_inventory'
/var/www/miq/vmdb/app/models/manageiq/providers/base_manager/refresher.rb:191:in `save_inventory'
/var/www/miq/vmdb/app/models/manageiq/providers/base_manager/refresher.rb:109:in `block in refresh_targets_for_ems'
/opt/rh/cfme-gemset/bundler/gems/cfme-gems-pending-71d6e5aabd0b/lib/gems/pending/util/extensions/miq-benchmark.rb:11:in `realtime_store'
/opt/rh/cfme-gemset/bundler/gems/cfme-gems-pending-71d6e5aabd0b/lib/gems/pending/util/extensions/miq-benchmark.rb:28:in `realtime_block'
/var/www/miq/vmdb/app/models/manageiq/providers/base_manager/refresher.rb:109:in `refresh_targets_for_ems'
/var/www/miq/vmdb/app/models/manageiq/providers/base_manager/refresher.rb:41:in `block (2 levels) in refresh'
/opt/rh/cfme-gemset/bundler/gems/cfme-gems-pending-71d6e5aabd0b/lib/gems/pending/util/extensions/miq-benchmark.rb:11:in `realtime_store'
/opt/rh/cfme-gemset/bundler/gems/cfme-gems-pending-71d6e5aabd0b/lib/gems/pending/util/extensions/miq-benchmark.rb:35:in `realtime_block'
/var/www/miq/vmdb/app/models/manageiq/providers/base_manager/refresher.rb:41:in `block in refresh'
/var/www/miq/vmdb/app/models/manageiq/providers/base_manager/refresher.rb:31:in `each'
/var/www/miq/vmdb/app/models/manageiq/providers/base_manager/refresher.rb:31:in `refresh'
/var/www/miq/vmdb/app/models/manageiq/providers/base_manager/refresher.rb:11:in `refresh'
/var/www/miq/vmdb/app/models/ems_refresh.rb:103:in `block in refresh'
/var/www/miq/vmdb/app/models/ems_refresh.rb:102:in `each'
/var/www/miq/vmdb/app/models/ems_refresh.rb:102:in `refresh'
/var/www/miq/vmdb/app/models/miq_queue.rb:455:in `block in dispatch_method'
/usr/share/ruby/timeout.rb:93:in `block in timeout'
/usr/share/ruby/timeout.rb:33:in `block in catch'
/usr/share/ruby/timeout.rb:33:in `catch'
/usr/share/ruby/timeout.rb:33:in `catch'
/usr/share/ruby/timeout.rb:108:in `timeout'
/var/www/miq/vmdb/app/models/miq_queue.rb:453:in `dispatch_method'
/var/www/miq/vmdb/app/models/miq_queue.rb:430:in `block in deliver'
/var/www/miq/vmdb/app/models/user.rb:275:in `with_user_group'
/var/www/miq/vmdb/app/models/miq_queue.rb:430:in `deliver'
/var/www/miq/vmdb/app/models/miq_queue_worker_base/runner.rb:104:in `deliver_queue_message'
/var/www/miq/vmdb/app/models/miq_queue_worker_base/runner.rb:137:in `deliver_message'
/var/www/miq/vmdb/app/models/miq_queue_worker_base/runner.rb:155:in `block in do_work'
/var/www/miq/vmdb/app/models/miq_queue_worker_base/runner.rb:149:in `loop'
/var/www/miq/vmdb/app/models/miq_queue_worker_base/runner.rb:149:in `do_work'
/var/www/miq/vmdb/app/models/miq_worker/runner.rb:329:in `block in do_work_loop'
/var/www/miq/vmdb/app/models/miq_worker/runner.rb:326:in `loop'
/var/www/miq/vmdb/app/models/miq_worker/runner.rb:326:in `do_work_loop'
/var/www/miq/vmdb/app/models/miq_worker/runner.rb:153:in `run'
/var/www/miq/vmdb/app/models/miq_worker/runner.rb:127:in `start'
/var/www/miq/vmdb/app/models/miq_worker/runner.rb:22:in `start_worker'
/var/www/miq/vmdb/app/models/miq_worker.rb:402:in `block in start_runner_via_fork'
/opt/rh/cfme-gemset/gems/nakayoshi_fork-0.0.4/lib/nakayoshi_fork.rb:23:in `fork'
/opt/rh/cfme-gemset/gems/nakayoshi_fork-0.0.4/lib/nakayoshi_fork.rb:23:in `fork'
/var/www/miq/vmdb/app/models/miq_worker.rb:400:in `start_runner_via_fork'
/var/www/miq/vmdb/app/models/miq_worker.rb:390:in `start_runner'
/var/www/miq/vmdb/app/models/miq_worker.rb:441:in `start'
/var/www/miq/vmdb/app/models/miq_worker.rb:271:in `start_worker'
/var/www/miq/vmdb/app/models/mixins/per_ems_worker_mixin.rb:74:in `start_worker_for_ems'
/var/www/miq/vmdb/app/models/mixins/per_ems_worker_mixin.rb:52:in `block in sync_workers'
/var/www/miq/vmdb/app/models/mixins/per_ems_worker_mixin.rb:51:in `each'
/var/www/miq/vmdb/app/models/mixins/per_ems_worker_mixin.rb:51:in `sync_workers'
/var/www/miq/vmdb/app/models/miq_server/worker_management/monitor.rb:53:in `block in sync_workers'
/var/www/miq/vmdb/app/models/miq_server/worker_management/monitor.rb:50:in `each'
/var/www/miq/vmdb/app/models/miq_server/worker_management/monitor.rb:50:in `sync_workers'
/var/www/miq/vmdb/app/models/miq_server/worker_management/monitor.rb:22:in `monitor_workers'
/var/www/miq/vmdb/app/models/miq_server.rb:339:in `block in monitor'
/opt/rh/cfme-gemset/bundler/gems/cfme-gems-pending-71d6e5aabd0b/lib/gems/pending/util/extensions/miq-benchmark.rb:11:in `realtime_store'
/opt/rh/cfme-gemset/bundler/gems/cfme-gems-pending-71d6e5aabd0b/lib/gems/pending/util/extensions/miq-benchmark.rb:28:in `realtime_block'
/var/www/miq/vmdb/app/models/miq_server.rb:339:in `monitor'
/var/www/miq/vmdb/app/models/miq_server.rb:380:in `block (2 levels) in monitor_loop'
/opt/rh/cfme-gemset/bundler/gems/cfme-gems-pending-71d6e5aabd0b/lib/gems/pending/util/extensions/miq-benchmark.rb:11:in `realtime_store'
/opt/rh/cfme-gemset/bundler/gems/cfme-gems-pending-71d6e5aabd0b/lib/gems/pending/util/extensions/miq-benchmark.rb:35:in `realtime_block'
/var/www/miq/vmdb/app/models/miq_server.rb:380:in `block in monitor_loop'
/var/www/miq/vmdb/app/models/miq_server.rb:379:in `loop'
/var/www/miq/vmdb/app/models/miq_server.rb:379:in `monitor_loop'
/var/www/miq/vmdb/app/models/miq_server.rb:241:in `start'
/var/www/miq/vmdb/lib/workers/evm_server.rb:27:in `start'
/var/www/miq/vmdb/lib/workers/evm_server.rb:48:in `start'
/var/www/miq/vmdb/lib/workers/bin/evm_server.rb:4:in `<main>'