LU-3756 mdt: Change HSM policy display

LU-3756 mdt: Change HSM policy display

HSM policy display must follow the format:
policy1 policy2 policy3 ... with [] around
active policies

Add sanity-hsm test 109 to test policy setting.

Signed-off-by: JC Lafoucriere <jacques-charles.lafoucriere@cea.fr>
Change-Id: I2000b9b8adfaf4cd2b369acbd076e65166832fc5
Reviewed-on: http://review.whamcloud.com/7365
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>