LU-6602 osp: change lgh_hdr_lock to mutex

LU-6602 osp: change lgh_hdr_lock to mutex

Change lgh_hdr_lock from spinlock to mutex, because in
osp_md_write_obj(), it might be blocked by memory
allocation.

Reorganize the llog_cache_rec process, so lgh_hdr_mutex
will protect both setbit and update llog header, to avoid
conflicts between add records and cancel llog records.

Signed-off-by: wang di <di.wang@intel.com>
Change-Id: Ic12d7d768546c67a858cb235929de8ae6aeaa1aa
Reviewed-on: http://review.whamcloud.com/15274
Tested-by: Jenkins
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>