nfsd: move name lookup out of nfsd4_list_rec_dir()

nfsd: move name lookup out of nfsd4_list_rec_dir()

nfsd4_list_rec_dir() is called with two different callbacks.
One of the callbacks uses vfs_rmdir() to remove the directory.
The other doesn't use the dentry at all, just the name.

As only one callback needs the dentry, this patch moves the lookup into
that callback.  This prepares of changes to how directory operations
are locked.

Signed-off-by: NeilBrown <neil@brown.name>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>