nfsd: move some commit_metadata()s outside the inode lock

[ Upstream commit eeeadbb9 ]

The commit may be time-consuming and there's no need to hold the lock
for it.

More of these are possible, these were just some easy ones.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>