engine: Datasource configuration fixes

Fix database configuration based on JBoss team suggestion. Allow to recover from DB failure.

Change-Id: Ib7cbe97f0baf85f8b6785726380a7a4dcb9d20f8
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=995084
Signed-off-by: lzelkha@redhat.com <liran.zelkha@gmail.com>