packaging: engine-backup.sh output db creation info

Add to '--help' instructions for creating a database and making it
accessible.

Change-Id: I212bfdd3b362880faa7aee159866d928de83d6f3
Bug-Url: https://bugzilla.redhat.com/1002401
Signed-off-by: Yedidyah Bar David <didi@redhat.com>