Add syslog tag to os-collect-config logs

We now have consistent os-collect-config log formats for both
fedora and ubuntu tripleo ci jobs(from systemd journal and syslog
respectively), see I27ea3d465670277ef1ddf3d1b3b9d52df4162807 and
Ib8c1fc39d56b2b9c6d8e9b64a868def619aa2f1f. Tagging them as syslog
will ensure they are handled by the logstash syslog grok filter,
they currently don't match anything which results in messages
being indexed with a value of "%{logmessage}".

Change-Id: Iec5ffcb08e5b45fb01db25e14c943f000ca97a83
Closes-Bug: #1350121
Merge "Add syslog tag to os-collect-config logs"