features/changelog: barrier all entry creation fops

when a snapshot is taken, there are chances of entry creation fops
not being recorded either in changelog or through the recursive
ancestry xtime updation by marker. This causes consumers of changelog
(primarily geo-replication as of today) to not be aware of these entries
after a snapshot is restored. This can lead to inconsistencies. This patch
is an interim workaround to barrier creates till changelog becomes completely
crash consistent.

BUG: 1128093
Change-Id: Ie0dbfd74beecb88df5c2ddf9fc680af91547c3f3
Signed-off-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-on: http://review.gluster.org/8517
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: ajeet jha <ajha@redhat.com>
Reviewed-by: Aravinda VK <avishwan@redhat.com>
Reviewed-by: Kotresh HR <khiremat@redhat.com>