LU-482 tests: cleanup clients/OSTs after MDS error

LU-482 tests: cleanup clients/OSTs after MDS error

If the MDS fails to mount due to LU-482, ensure that the clients
and OSTs are unmounted cleanly.  Otherwise, the normal unmount
will hang on the clients as they wait for the MDS to be recovered.

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Iccd8f81f714974063eaeec45ffbd80f9cef3242b
Reviewed-on: http://review.whamcloud.com/3019
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>