libglusterfs: Propositions should be logical

Mutually exclusive tests shouldn't be
non-contradictory
 -- (A is B) && (A is not B) is not valid

Change-Id: Icf97d1704fedca4b8eeeb67da8b7d4c8d4b578d5
BUG: 769692
Signed-off-by: Harshavardhana <harsha@harshavardhana.net>
Reviewed-on: http://review.gluster.org/6115
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>