LU-13238 ofd: add OFD access logs

LU-13238 ofd: add OFD access logs

Add access logs to OFD layer. BRW RPC handlers will record accesss to
an in memory circular buffer which may be read in userspace through
character devices (/dev/lustre-access-log/$FSNAME-OSTxxxx). A control
device (/dev/lustre-access-log/control) is added to facilitate device
discovery. A utility (ofd_access_log_reader) to discover and consume
access logs is included.

Signed-off-by: John L. Hammond <jhammond@whamcloud.com>
Change-Id: I76b78cc5075ee01f9b234e96e7a22a1bdcf2f755
Reviewed-on: https://review.whamcloud.com/37552
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Gu Zheng <gzheng@ddn.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>