rpc_workers can be set < 1 with 'ovn' backend when no
other agent is running apart from ovn agents to
consume these rpc notifications.
Add and apply disable_notifications decorator on
methods which do rpc cast calls to agents, the
decorator makes the caller method execute only
when rpc_workers >=1. This patch not changing
default behavior and utilizes the rpc_workers config option
to enable rpc notification on resources updates only when
rpc_workers >= 1.
Also set rpc_workers=0 in ovn jobs to cover this scenario.
Closes-Bug: #1889737
Closes-Bug: #1992352
Change-Id: I700fe2cd422bc1eb8b5144ec116e7f0a60238419
yatinkarel
3e1e2d63b3