Tests: Test functionality of flush/fsync with afr

Change-Id: I307a77e90e1852f5e43d50e347f7b52468105389
BUG: 888174
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/4447
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>