core: fix db restore usage comment

If the restore.sh is invoked with a DB name that is different than the
name appearing in the backup file, restore will fail.

this patch only added this information to the script usage comments.

Change-Id: Ibe11f2684c72686d183323c96f73a86d6cf1f8ea
Signed-off-by: Eli Mesika <emesika@redhat.com>