engine: Log detection of orphan gluster tasks

When tasks no longer exist in gluster CLI,
these are marked as Unknown and ended.
Added audit log for these.

Change-Id: Ia9cc4658dc4ed5700ce93463f4480d65e7d71c12
Bug-Url: https://bugzilla.redhat.com/1040973
Signed-off-by: Sahina Bose <sabose@redhat.com>