pNFS/files: Fix layoutcommit after a commit to DS

According to the errata
https://www.rfc-editor.org/errata_search.php?rfc=5661&eid=2751
we should always send layout commit after a commit to DS.

Fixes: bc7d4b8f

 ("nfs/filelayout: set layoutcommit...")
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>