Send mcollective logs to syslog as well

- Use rsyslog::imfile to track mco logs as syslog daemon/debug ones
- Drop duplicating mco/nailgun-agent messages targeted to syslog files
- Add nailgun-agent.log to log rotation plans as well.

Partial blueprint: collect-mco-and-agent-logs-with-shotgun

Change-Id: I95c6e04bd1f647ea655647223bffffe9b4e7a8a8
Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>
Merge "Send mcollective logs to syslog as well"