NFS is picking up geo-rep's already open (read-only) file descriptor

Add anonymous member to fd_t and use it instead of over-loading pid for
geo-rep and self heal

Change-Id: I4d6b29a044a8ed4b8f69ff6e3f35ee227739b2af
Signed-off-by: Kaleb S. KEITHLEY <kkeithle@redhat.com>
BUG: 874272
Reviewed-on: http://review.gluster.org/4185
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Raghavendra Bhat <raghavendra@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-on: http://review.gluster.org/5283