protocol/server: No root-squash checks for self-heal pid

Problem:
Self-heal pid used to be -1 which was colliding with gsyncd. Gsyncd
was not checked for root-squash authentication. Recently self-heal
pid changed to -6, but root-squash authentication is not disabled
for this.

Fix:
disable root-squash authentication for self-heal

Change-Id: I93233d4ae681cb936d166b22992eb47c658ea977
BUG: 1170407
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/9231
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>