LU-4647 tests: properly cleanup after test failure

LU-4647 tests: properly cleanup after test failure

If test_16 fails all subsequent tests will fail also because of
improper cleanup after errors. Add cleanup in case of failure.

Change-Id: If828ad0e908c4f65be6f41f57fe14fb23801b2ed
Signed-off-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-on: http://review.whamcloud.com/14933
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>