LU-10488 tests: saved and restore layout for dom test

LU-10488 tests: saved and restore layout for dom test

Some features like FLR and quota are still not supported by dom.
It will cause failures when dom is enabled when the corresponding
test cases are running.

This patch saves and restores default layout before and after
sanity-dom runs.

Test-Parameters: trivial envdefinitions=SLOW=yes,ENABLE_QUOTA=yes testlist=sanity-dom,sanity-flr,sanity-quota
Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Change-Id: I69752c3c48e3edf32ff22399af32b67c718f8e0e
Reviewed-on: https://review.whamcloud.com/30836
Tested-by: Jenkins
Reviewed-by: James Nunez <james.a.nunez@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>