When a VM is rebooted and it has a port in a Neutron trunk with DPDK and
vhostuserclient mode, Nova will delete the OVS port and then recreate it
when the VM reboots. This quick transition can create a race condition
whereby Neutron deletes the trunk's bridge between the interface removal
and addition by os-vif, so the latter operation fails because the bridge
doesn't exist anymore. To fix this, ensuring the bridge existance and
the vif addition becomes an atomic operation from the point of view of
the OVSDB transaction.
This change is associated to [1] on the Neutron side.
[1] https://review.opendev.org/c/openstack/neutron/+/829139
Partial-Bug: #1869244
Change-Id: Id7ece4ebc9239d9776c43b8d7f9e82b0319a08c6
21b076e7df