Force chown for log files before starting rabbitmq

For some reason log files /var/log/rabbitmq/startup_log and
/var/log/rabbitmq/shutdown_log becomes owned be root,
preventing rabbitmq-server for murano (launched from 'rabbitmq' user)
from writing to them.

Change-Id: Ifa3d3484e3f22fe97cdb747c2c58f2d408246f32
Closes-bug: #1360264
Merge "Force chown for log files before starting rabbitmq"