LU-10699 hsm: simplify mdt_hsm_{add,get}_actions()

LU-10699 hsm: simplify mdt_hsm_{add,get}_actions()

Split the mdt_hsm_get_actions() functionality of
hsm_find_compatible_cb() into a new llog callback
(hsm_find_action_cb()). Simplify hsm_find_compatible() since it only
needs to handle adding new requests. Simplify the MDS_HSM_ACTIONS
handling code.

Test-Parameters: trivial testlist=sanity-hsm
Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: Ie1e7eac85397d82ad9cc4790582bf8ba51713e70
Reviewed-on: https://review.whamcloud.com/31385
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Faccini Bruno <bruno.faccini@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>