LU-11114 llite: Update mdc and lite stats on open|creat

LU-11114 llite: Update mdc and lite stats on open|creat

Increment "create" counter in mdc/<instance>/md_stats, and
"mknod" counter in llite/<instance>stats when an open with
the CREAT flag results in a newly created file.

The mknod counter is chosen for consistency with
patch http://review.whamcloud.com/20246
 "LU-8150 mdt: Track open+create as mknod"
but the mdc counter set does not include mknod.

Lustre-change: https://review.whamcloud.com/36948
Lustre-commit: 4b8518ee4fa542f45fcdaeaec580d858dfcaf137

Signed-off-by: Olaf Faaland <faaland1@llnl.gov>
Change-Id: If082b911e415c0bc46248728e47ce0f37b9efa83
Reviewed-on: https://review.whamcloud.com/38158
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Emoly Liu <emoly@whamcloud.com>