gluster: compare GlusterAsyncTask in equals of Entities

Added GlusterAsyncTask comparison to GlusterVolumeEntity's
and GlusterBrickEntity's equals method.

Change-Id: If85362b23057532ba69fe2b9f6d0e9c5d5753e2b
Bug-Url: https://bugzilla.redhat.com/1025013
Signed-off-by: Kanagaraj M <kmayilsa@redhat.com>