Replace the always-true check tcon->origin_fullpath with
check of server->leaf_fullpath

See https://bugzilla.kernel.org/show_bug.cgi?id=219083

The check of the new @tcon will always be true during mounting,
since @tcon->origin_fullpath will only be set after the tree is
connected to the latest common resource, as well as checking if
the prefix paths from it are fully accessible.

Fixes: 3ae872de ("smb: client: fix shared DFS root mounts with different prefixes")
Reviewed-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
Signed-off-by: Gleb Korobeynikov <gkorobeynikov@astralinux.ru>
Signed-off-by: Steve French <stfrench@microsoft.com>