features/changelog: Capture "correct" internal FOPs

This patch fixes changelog capturing internal FOPs in a cascaded
setup, where the intermediate master would record internal FOPs
(generated by DHT on link()/rename()). This is due to I/O happening
on the intermediate slave on geo-replication's auxillary mount with
client-pid -1. Currently, the internal FOP capturing logic depends
on client pid being non-negative and the presence of a special key
in dictionary. Due to this, internal FOPs on an inter-mediate master
would be recorded in the changelog. Checking client-pid being
non-negative was introduced to capture AFR self-heal traffic in
changelog, thereby breaking cascading setups. By coincidence,
AFR self-heal daemon uses -1 as frame->root->pid thereby making
is hard to differentiate b/w geo-rep's auxillary mount and self-heal
daemon.

BUG: 1138952
Change-Id: Ia08a2cfa3b02bb785f343794f5b2695d44398c4c
Original-Author: Venky Shankar <vshankar@redhat.com>
Signed-off-by: Kotresh H R <khiremat@redhat.com>
Reviewed-on: http://review.gluster.org/8347
Reviewed-by: Venky Shankar <vshankar@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-on: http://review.gluster.org/8638