LU-2675 obd: cleanup struct md_op_data and uses

LU-2675 obd: cleanup struct md_op_data and uses

Make the following changes in or around struct md_op_data:

* Move the definition of enum op_cli_flags from lclient.h to obd.h and
  rename it to enum md_cli_flags.

* Change to type of the op_flags member from __u32 to enum
  md_op_flags.

* Remove the used but never set member op_npages.

* Remove the set but never used member op_stripe_offset (an alias for
  op_ioepoch).

* Remove the op_max_pages alias for op_valid and add a op_max_pages
  member.

* Add a new member op_attr_flags.

* Remove the definition and all uses of struct ll_iattr. This
  structure was only used in expressions of the form
  ((struct ll_iattr *)&op_data->op_attr)->ia_attr_flags which can all
  be rewritten as op_data->op_attr_flags.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: I17aabfcecdfd1a02dbee04362b033ef404a2cb27
Reviewed-on: http://review.whamcloud.com/11734
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>