Moved closing of fd1 to the inner try block in the test_do_write_err function.

This is a follow up change to the previous commit to fs_utils unit test case
patch.

Change-Id: I677683677071efc6176ad2145d1806bc7e658c9e
Signed-off-by: Mohammed Junaid <junaid@redhat.com>
Reviewed-on: http://review.gluster.org/5116
Reviewed-by: Peter Portante <pportant@redhat.com>
Tested-by: Peter Portante <pportant@redhat.com>