When the Neutron WSGI module is used, an independent service called
"neutron-rpc-server" is configured and executed. However it will fail
if the number of RPC workers is configured to zero. In that case,
the configuration and execution of this service should be skipped.
If the service is explicitly disabled in the devstack configuration,
it won't be executed neither.
Closes-Bug: #2073572
Change-Id: Idd023a2a8f588152221f20a13ae24fbb7d1618a4
aaaa03718b