engine : query execution failed due to insufficient permissions

Adding a disk using a user with DiskCreator
privileges logs insufficient permissions
message in the log

Change-Id: I11adfe9c49d1e57ecc88d1828ed63884016c33e8
Bug-Url: https://bugzilla.redhat.com/1153043
Signed-off-by: Ravi Nori <rnori@redhat.com>