LU-3017 tests: sanityn: remove all previous test run data

LU-3017 tests: sanityn: remove all previous test run data

Ensure all previous data from sanityn is removed.  Test 3 would fail
if it's previous data was still present in the filesystem.

Signed-off-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Change-Id: If4aba05e0d78b49ab5e799dea83aa5815f43f20e
Reviewed-on: http://review.whamcloud.com/5810
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Keith Mannthey <keith.mannthey@intel.com>
Tested-by: Hudson
Reviewed-by: Li Wei <wei.g.li@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>