Description of problem:
When few VMs are created simultaneously, customer faces a weird problem in RHOSP 17.1.3 ML2/OVS deployment: network-vif-plugged messages are not sent by neutron-server. From collected logs it looks like it is stuck waiting for ack from DHCP agents, but DHCP agents don't log anything related to new port.

Version-Release number of selected component (if applicable): RHOSP 17.1.3

How reproducible: customer uses Nova interface to create few VMs in the same networks

Actual results: some VMs fail to start because Nova faces 300 sec time out while waiting for network-vif-plugged message

Expected results: VMs are started after interfaces are plugged successfully

Log extracts will be provided privately.