pNFS: Actively set attributes as invalid if LAYOUTCOMMIT is outstanding

A LAYOUTCOMMIT then subsequent GETATTR may both return the same attributes,
and in that case NFS_INO_INVALID_ATTR is never set on the second pass
through nfs_update_inode().  The existing check to skip the clearing of
NFS_INO_INVALID_ATTR if a LAYOUTCOMMIT is outstanding does not help in this
case (see commit 10b7e9ad

: "pNFS: Don't mark the inode as revalidated
if a LAYOUTCOMMIT is outstanding").  We know that if a LAYOUTCOMMIT is
outstanding then attributes will need upating, so always set
NFS_INO_INVALID_ATTR.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>