Final forward port of PDQ performance patches

Change-Id: I4ef131b3cc7648d4571a4d854029efb1aff8b901
Signed-off-by: Peter Portante <peter.portante@redhat.com>
Reviewed-on: http://review.gluster.org/5305
Reviewed-by: Luis Pabon <lpabon@redhat.com>
Tested-by: Luis Pabon <lpabon@redhat.com>