Don't translate debug level logs in nova.network

Our translation policy
(https://wiki.openstack.org/wiki/LoggingStandards#Log_Translation) calls
for not translating debug level logs. This is to help prioritize log
translation. Furthermore translation has a performance overhead, even if
the log isn't used (since nova doesn't support lazy translation yet).

Change-Id: I8973992d0dd2348f9c657c3caa1cc9c7d79a4c7b
Merge "Don't translate debug level logs in nova.network"