LU-3876 hsm: proc agent_actions fix up

LU-3876 hsm: proc agent_actions fix up

In the original implementation, it will return ENOMEM if there
exists too many llog entries.

Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Change-Id: I48089bae566f28fd0128f749ce1581b1fc26d45b
Reviewed-on: http://review.whamcloud.com/7589
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: jacques-Charles Lafoucriere <jacques-charles.lafoucriere@cea.fr>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>