LU-3852 tests: remove large files created by HSM test

Delete files created by HSM test cases with size bigger than 10M.

Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Change-Id: Ibe774254110d0d6f3477bd0bbb3bf287c4356b9a
Reviewed-on: http://review.whamcloud.com/7484
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: jacques-Charles Lafoucriere <jacques-charles.lafoucriere@cea.fr>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>