LU-2833 tests: Unexempt sanity/48a for zfs

LU-2833 tests: Unexempt sanity/48a for zfs

With LU-2449 being landed this test no longer fails on ZFS.

Signed-off-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Change-Id: Ie82f25ac0152dee7972a8a210d8669b59798e9a7
Reviewed-on: http://review.whamcloud.com/12607
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Isaac Huang <he.huang@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>