LU-9219 tests: add missing mgs reformat to conf-sanity/56

LU-9219 tests: add missing mgs reformat to conf-sanity/56

conf-sanity/test_56 timedout while mounting client
the reason of timeout is mounting mds failed with -EADDRINUSE.
Registering mdt to MGS while mounting mds index of server was
already present in MGS configuration database so mds mount
failed with -EADDRINUSE and further test stuck while client
mount so test timedout.

This change adds missing mgs reformat when mgs and mds
separate before starting mdt and osts, This will make sure
index of mdt will not be present in MGS config database.

Seagate-bug-id: MRP-3806
Signed-off-by: Jadhav Vikram <jadhav.vikram@seagate.com>
Reviewed-by: Vladimir Saveliev <vladimir.saveliev@seagate.com>
Reviewed-by: Alexandr Boyko <alexander.boyko@seagate.com>
Tested-by: Elena V. Gryaznova <elena.gryaznova@seagate.com>
Change-Id: Ie7d897534197af7e01d92d29613123a0290ffc4c
Reviewed-on: https://review.whamcloud.com/26029
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Alexander Boyko <alexander.boyko@seagate.com>
Tested-by: Jenkins
Reviewed-by: Emoly Liu <emoly.liu@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>