core:restore.sh fails to drop existing database...

restore.sh fails to drop existing database and continues running

Adding a check on the dropdb command status and existing if not
succeeded.

Change-Id: If9d33e0011cdac6bb0d9b153cc4f4a118c7b4aaf
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=929359
Signed-off-by: Eli Mesika <emesika@redhat.com>