packaging: add timestamps to engine-db-install logs

Added new function logmsg that add a timestamp to the message that
will be logged.
Refactored the code for using logmsg for writing log messages.

Change-Id: I2ed2bfd889da31ee4626365653d9ea2dee37fd9f
Bug-Url: https://bugzilla.redhat.com/885611
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>