LU-3485 tests: add resize2fs testing for MDT and OST filesystems

LU-3485 tests: add resize2fs testing for MDT and OST filesystems

This patch adds a test case into conf-sanity.sh to test running
resize2fs on MDT and OST filesystems. Currently, only offline
resizing is possible until LU-137 is finished. Before and after
resize2fs is used, e2fsck is run to verify that no corruption
is introduced during the process.

Signed-off-by: Jian Yu <jian.yu@intel.com>
Change-Id: I0957cba7fdd76276331c40b746cd87efac10ecc4
Reviewed-on: http://review.whamcloud.com/7796
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>