LU-2852 script: sanity 27u should cleanup test dir

LU-2852 script: sanity 27u should cleanup test dir

sanity 27u should cleanup test dir before test in case there
are remaining files from previous tests.

remove 27u from ALWAYS_EXCEPT since it can pass now.

Signed-off-by: Lai Siyao <lai.siyao@intel.com>
Change-Id: Id21589c1e1ecf0f4143fad3574cd779c73adb7aa
Reviewed-on: http://review.whamcloud.com/5670
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>