cifs: don't refresh cached referrals from unactive mounts

There is no point refreshing cached referrals from unactive mounts as
they will no longer be used and new mounts will either create or
refresh them anyway.

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>