LU-10948 mdt: Remove openlock compat code with 2.1

LU-10948 mdt: Remove openlock compat code with 2.1

Checking openlock when doing a create does not allow us to create
a file if we want to also get openlock from it right away.

Since 2.1 is no longer something we care about wrt compatibility,
ok to kill it.

Change-Id: Ic4327be5c45ae856dfbe20291a59c5b1654dbf8f
Signed-off-by: Oleg Drokin <green@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/35039
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>