LU-9312 hsm: add a cookie indexed request hash

LU-9312 hsm: add a cookie indexed request hash

Replace linear scans of the HSM coordinator's cdt_requests list with
lookups into a cookie indexed hash (cdt_request_cookie_hash). Rename
cdt_requests to cdt_request_list. Remove the unused function
mdt_hsm_get_running().

Change-Id: I97309aeeb0e02a07e8ddac9f1667989c65f01b8b
Signed-off-by: John L. Hammond <john.hammond@intel.com>
Reviewed-on: https://review.whamcloud.com/26763
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Henri Doreau <henri.doreau@cea.fr>
Reviewed-by: Faccini Bruno <bruno.faccini@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>