LU-3726 tests: make sanity-hsm compatible with MDSCOUNT >= 2.

LU-3726 tests: make sanity-hsm compatible with MDSCOUNT >= 2.

Add generic functions to perform set_param and check_param
on all MDTs, and persistent set_param on the mgs.
CL_USER variable replaced by CL_USERS array (1 value per MDT).
MDT0 variable replaced by MDT array (1 value per MDT).

Test-Parameters: mdtcount=2 mdscount=2 testlist=sanity-hsm
Signed-off-by: Thomas Leibovici <thomas.leibovici@cea.fr>
Signed-off-by: Aurelien Degremont <aurelien.degremont@cea.fr>
Change-Id: I0d8610a74427423dda25a6defd85f5c52c535850
Reviewed-on: http://review.whamcloud.com/7437
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: jacques-Charles Lafoucriere <jacques-charles.lafoucriere@cea.fr>
Reviewed-by: Faccini Bruno <bruno.faccini@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>