Description of problem:
When creating lots of VMs, sometimes the following error message is encountered and VM creation errors:

2019-07-18 19:32:05.151 34 ERROR ovsdbapp.backend.ovs_idl.transaction [-] OVSDB Error: {"details":"insert operation not allowed when database server is in read only mode","error":"not allowed"}:
 RuntimeError: OVSDB Error: {"details":"update operation not allowed when database server is in read only mode","error":"not allowed"}
2019-07-18 19:32:05.151 34 ERROR ovsdbapp.backend.ovs_idl.transaction [req-44f89b8e-c647-41cb-bd62-9b62554a042e 70bfd15a9f9a3f32a589a3cfcbcb78886d3be060e961dd38048eef87870202a9 01b728e67a5a4d88b
655e5b3bc232450 - 0ef23cf14b4a4cecade7d9f1cee1862b 0ef23cf14b4a4cecade7d9f1cee1862b] Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/ovsdbapp/backend/ovs_idl/connection.py", line 99, in run
    txn.results.put(txn.do_commit())
  File "/usr/lib/python2.7/site-packages/ovsdbapp/backend/ovs_idl/transaction.py", line 115, in do_commit
    raise RuntimeError(msg)
RuntimeError: OVSDB Error: {"details":"insert operation not allowed when database server is in read only mode","error":"not allowed"}

2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers [req-44f89b8e-c647-41cb-bd62-9b62554a042e 70bfd15a9f9a3f32a589a3cfcbcb78886d3be060e961dd38048eef87870202a9 01b728e67a5a4d88b655e5b3bc232450 - 0ef23cf14b4a4cecade7d9f1cee1862b 0ef23cf14b4a4cecade7d9f1cee1862b] Mechanism driver 'ovn' failed in create_port_postcommit: RuntimeError: OVSDB Error: {"details":"insert operation not allowed when database server is in read only mode","error":"not allowed"}
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers Traceback (most recent call last):
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers   File "/usr/lib/python2.7/site-packages/neutron/plugins/ml2/managers.py", line 427, in _call_on_drivers
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers     getattr(driver.obj, method_name)(context)
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers   File "/usr/lib/python2.7/site-packages/networking_ovn/ml2/mech_driver.py", line 476, in create_port_postcommit
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers     self._ovn_client.create_port(port)
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers   File "/usr/lib/python2.7/site-packages/networking_ovn/common/ovn_client.py", line 350, in create_port
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers     self.add_txns_to_sync_port_dns_records(txn, port)
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers   File "/usr/lib64/python2.7/contextlib.py", line 24, in __exit__
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers     self.gen.next()
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers   File "/usr/lib/python2.7/site-packages/networking_ovn/ovsdb/impl_idl_ovn.py", line 139, in transaction
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers     yield t
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers   File "/usr/lib64/python2.7/contextlib.py", line 24, in __exit__
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers     self.gen.next()
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers   File "/usr/lib/python2.7/site-packages/ovsdbapp/api.py", line 102, in transaction
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers     del self._nested_txns_map[cur_thread_id]
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers   File "/usr/lib/python2.7/site-packages/ovsdbapp/api.py", line 59, in __exit__
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers     self.result = self.commit()
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers   File "/usr/lib/python2.7/site-packages/ovsdbapp/backend/ovs_idl/transaction.py", line 62, in commit
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers     raise result.ex
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers RuntimeError: OVSDB Error: {"details":"insert operation not allowed when database server is in read only mode","error":"not allowed"}
2019-07-18 19:32:05.152 34 ERROR neutron.plugins.ml2.managers 


Version-Release number of selected component (if applicable):
Latest

How reproducible:
Sometimes

Steps to Reproduce:
1. Create a bunch of VMs like 80
2. Rince and repeat until you hit that issue
3.

Actual results:
VM is in error

Expected results:
VM should be created

Additional info: