LU-168 Fix schedule race in sanityn PDO lock tests

LU-168 Fix schedule race in sanityn PDO lock tests

In sanityn PDO lock tests, even if the second operation is blocked by
the first one on server-side, after the blocking, the second one may
be finished earlier than the first one because of client-side schedule
order. So sleep a sec before check_pdo_conflict() to ensure the first
operation is finished after OBD_FAIL_MDS_PDO_LOCK barriers.

Change-Id: I62412d74e17be012ee6660179ad77375c196671d
Signed-off-by: nasf <yong.fan@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/1030
Tested-by: Hudson
Reviewed-by: Mikhail Pershin <tappro@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>