LU-6142 lustre: change various operations structs to const

LU-6142 lustre: change various operations structs to const

Nearly all of
  struct cl_io_operations
  struct cl_lock_operations
  struct iam_operations
  struct iam_leaf_operations
  struct llog_operations
  struct lquota_entry_operations
  struct md_dir_operations

are now const.  The one exception is changelog_orig_logops.

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I91dc9528b62a77f6bcedc80d6066a74a8eeaa3fa
Reviewed-on: https://review.whamcloud.com/39400
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>