Description of problem:
When creating an IPv6 only host, the process will fail with the following error:
  Unable to render PXEGrub2 template 'Kickstart default PXEGrub2': undefined method '#httpboot' for NilClass::Jail (NilClass)

Version-Release number of selected component (if applicable):
Sat 6.8 Snap 8

How reproducible:
always

Steps to Reproduce:
Same steps as in BZ1848535. 

Actual results:
The host is not created.

Expected results:
The host is created.

Additional info:
This issue was discovered while verifying the fix for BZ1848535. The workaround is similar - create the host with only an IPv4 network assigned. It will be created successfully, and then you can remove the IPv4 network from it, and assign an IPv6 network instead. It seems the issue in BZ1848535 was actually fixed, the creation process proceeds to a next phase, and fails there.

production.log contains following output: 

2020-07-14T10:17:52 [I|app|0c0276d2] Started GET "/notification_recipients" for 127.0.0.1 at 2020-07-14 10:17:52 -0400
2020-07-14T10:17:52 [I|app|0c0276d2] Processing by NotificationRecipientsController#index as JSON
2020-07-14T10:17:52 [I|app|0c0276d2] Completed 200 OK in 12ms (Views: 0.1ms | ActiveRecord: 1.7ms | Allocations: 2169)
2020-07-14T10:17:52 [I|app|2b8c1a75] Started POST "/hosts" for 127.0.0.1 at 2020-07-14 10:17:52 -0400
2020-07-14T10:17:52 [I|app|2b8c1a75] Processing by HostsController#create as */*
2020-07-14T10:17:52 [I|app|2b8c1a75]   Parameters: {"utf8"=>"✓", "authenticity_token"=>"vua0iJFdp5TZFloh9YpGxLPU1S4V5XT9k9iDZC6xbAidBjuf6zVYhlALPvw/keWlqwQi6kiK6Ya24AcOpXgL7g==", "host"=>{"name"=>"kerri-petiet", "organization_id"=>"1", "location_id"=>"2", "hostgroup_id"=>"", "compute_resource_id"=>"", "content_facet_attributes"=>{"lifecycle_environment_id"=>"1", "content_view_id"=>"1", "content_source_id"=>"1", "kickstart_repository_id"=>"7"}, "environment_id"=>"", "puppet_proxy_id"=>"", "puppet_ca_proxy_id"=>"", "openscap_proxy_id"=>"", "ansible_role_ids"=>[""], "managed"=>"true", "progress_report_id"=>"[FILTERED]", "type"=>"Host::Managed", "interfaces_attributes"=>{"0"=>{"_destroy"=>"0", "type"=>"Nic::Managed", "mac"=>"52:54:00:47:05:9a", "identifier"=>"", "name"=>"kerri-petiet", "domain_id"=>"2", "subnet_id"=>"", "subnet6_id"=>"1", "ip"=>"", "ip6"=>"fd00:aaaa:bbbb:cc:5054:ff:fe47:59a", "managed"=>"1", "primary"=>"1", "provision"=>"1", "execution"=>"1", "virtual"=>"0", "tag"=>"", "attached_to"=>""}}, "architecture_id"=>"1", "operatingsystem_id"=>"3", "provision_method"=>"build", "build"=>"1", "medium_id"=>"", "ptable_id"=>"116", "pxe_loader"=>"Grub2 UEFI HTTP", "disk"=>"", "root_pass"=>"[FILTERED]", "is_owned_by"=>"4-Users", "enabled"=>"1", "model_id"=>"", "comment"=>"", "overwrite"=>"false"}, "media_selector"=>"synced_content"}
2020-07-14T10:17:53 [I|app|2b8c1a75] Deploying TFTP PXELinux configuration for kerri-petiet.example.com
2020-07-14T10:17:53 [W|app|2b8c1a75] Unable to render PXEGrub2 template 'Kickstart default PXEGrub2': undefined method '#httpboot' for NilClass::Jail (NilClass)
2020-07-14T10:17:53 [I|app|2b8c1a75] Skipping TFTP PXEGrub2 configuration for kerri-petiet.example.com
2020-07-14T10:17:53 [I|app|2b8c1a75] Deploying TFTP PXEGrub configuration for kerri-petiet.example.com
2020-07-14T10:17:53 [I|app|2b8c1a75] Deploying TFTP iPXE configuration for kerri-petiet.example.com
2020-07-14T10:17:53 [I|app|2b8c1a75] Fetching required TFTP boot files for kerri-petiet.example.com
2020-07-14T10:17:54 [W|app|2b8c1a75] Rolling back due to a problem: []
2020-07-14T10:17:54 [I|app|2b8c1a75] Delete the TFTP configuration for kerri-petiet.example.com
2020-07-14T10:17:54 [I|app|2b8c1a75] Delete the TFTP configuration for kerri-petiet.example.com
2020-07-14T10:17:54 [I|app|2b8c1a75] Delete the TFTP configuration for kerri-petiet.example.com
2020-07-14T10:17:54 [I|app|2b8c1a75] Delete the TFTP configuration for kerri-petiet.example.com
2020-07-14T10:17:54 [I|app|2b8c1a75] Processed 5 tasks from queue 'Host::Managed Main', completed 0/5
2020-07-14T10:17:54 [E|app|2b8c1a75] Task 'Deploy TFTP PXELinux config for kerri-petiet.example.com' *rollbacked*
2020-07-14T10:17:54 [E|app|2b8c1a75] Task 'Deploy TFTP PXEGrub2 config for kerri-petiet.example.com' *rollbacked*
2020-07-14T10:17:54 [E|app|2b8c1a75] Task 'Deploy TFTP PXEGrub config for kerri-petiet.example.com' *rollbacked*
2020-07-14T10:17:54 [E|app|2b8c1a75] Task 'Deploy TFTP iPXE config for kerri-petiet.example.com' *rollbacked*
2020-07-14T10:17:54 [E|app|2b8c1a75] Task 'Fetch TFTP boot files for kerri-petiet.example.com' *rollbacked*
2020-07-14T10:17:54 [E|app|2b8c1a75] Failed to save: Unable to render PXEGrub2 template 'Kickstart default PXEGrub2': undefined method '#httpboot' for NilClass::Jail (NilClass)
2020-07-14T10:17:54 [I|app|2b8c1a75]   Rendering hosts/new.html.erb within layouts/application
2020-07-14T10:17:54 [I|app|2b8c1a75]   Rendered hosts/_progress.html.erb (Duration: 4.6ms | Allocations: 7116)
2020-07-14T10:17:54 [I|app|2b8c1a75]   Rendered /opt/theforeman/tfm/root/usr/share/gems/gems/katello-3.16.0.rc4/app/views/overrides/activation_keys/_host_environment_select.html.erb (Duration: 15.8ms | Allocations: 10758)
2020-07-14T10:17:54 [I|app|2b8c1a75]   Rendered hosts/puppet/_main_tab_fields.html.erb (Duration: 13.3ms | Allocations: 9454)