LU-1233 tests: clean up files in performance-sanity test

LU-1233 tests: clean up files in performance-sanity test

This patch cleans up the files created in performance-sanity.sh
through mdsrate-{create,lookup,stat}-*.sh after create/lookup/stat
operation fails.

Test-Parameters: envdefinitions=SLOW=yes,ENABLE_QUOTA=yes \
clientdistro=el6 serverdistro=el6 clientarch=x86_64 \
serverarch=x86_64 testlist=performance-sanity

Signed-off-by: Jian Yu <jian.yu@intel.com>
Change-Id: I2fc612bea7a10dd7bb5a735af2b1330f339c2a22
Reviewed-on: http://review.whamcloud.com/6483
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Minh Diep <minh.diep@intel.com>
Reviewed-by: Wei Liu <wei3.liu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>