Move mongodb logs to mongod.log

Enables consolidation of MongoDB logs in one location,
instead of polluting /var/log/messages.

Added rotation for /var/log/mongod.log on deployed nodes,
while the current Fuel Master rotation requires no changes.

Change-Id: I3bbc6b87ed9d125191041c310069136c59d8d1f9
Closes-Bug: 1367234
Merge "Move mongodb logs to mongod.log"