api: Fill loc.path and loc.gfid before syncop_open.

syncop_open was crashing because of NULL dereference.
This fixes that.

Change-Id: I4bc48fac2a6c0b15c806cbbb4ae45c67891ab7ed
BUG: 1002577
Signed-off-by: Raghavendra Talur <rtalur@redhat.com>
Reviewed-on: http://review.gluster.org/5877
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>