LU-6198 test: fix large-lun test_1, test_2 defects

LU-6198 test: fix large-lun test_1, test_2 defects

setupall()->start ost called at the end of large-lun.sh
fails to start the ost devices which leads test_1() and
test_2() fail if run separately.

The reasons are:
1) osts data are destroyed by test_1()->llverdev
2) osts are reformatted by test_2, but mds config not changed
Patch fixes the following:
- format Lustre at the end of test_1() and test_2()
- add the "REFORMAT" option check to avoid killing
filesystems that do not want a reformat.

Signed-off-by: Elena Gryaznova <elena.gryaznova@seagate.com>
Xyratex-bug-id: MRP-1984
Reviewed-by: Vladimir Saveliev <vladimir.saveliev@seagate.com>
Change-Id: I7f1465d4777b7a5d5538e019226334dc090e3f50
Reviewed-on: http://review.whamcloud.com/13601
Reviewed-by: Emoly Liu <emoly.liu@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>