testcase for the open-behind xlator when open fails

Test if the fops which are put into a stub and are waiting for
the open to complete should be unwound with the error if open
call itself fails.

Change-Id: I8c363d98303a7df1a0ca9ea6ef207c7123fdd388
BUG: 846240
Signed-off-by: Raghavendra Bhat <raghavendra@redhat.com>
Reviewed-on: http://review.gluster.org/4553
Reviewed-by: Anand Avati <avati@redhat.com>
Tested-by: Anand Avati <avati@redhat.com>