Avoid refreshing DFS referral with refpath_lock acquired as the I/O
could block for a while due to a potentially disconnected or slow DFS
root server and then making other threads - that use same @server and
don't require a DFS root server - unable to make any progress.

Cc: stable@vger.kernel.org # 6.4+
Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>