gfapi: store the open/create flags in fd_t object

The flags passed on to open and create calls were not being saved
in the fd_t object, hence the fd migration was failing.

Change-Id: I486bb818477fe4c393d64a711534a082162a0e53
BUG: 1005159
Signed-off-by: Poornima <pgurusid@redhat.com>
Reviewed-on: http://review.gluster.org/5873
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>