remote: fix UNIX socket path being incorrectly built for libvirtd

As a result of changes in

commit d5f0c1b6dd51f0fbab2f8a25733c55d8be6b937b
Author: Daniel P. Berrangé <berrange@redhat.com>
Date: Thu Jul 18 12:30:22 2019 +0100

remote: stop trying to print help as giant blocks of text

The socket path built would be libvirt//var/run/libvirt-sock
instead of /var/run/libvirt/libvirt-sock. Fortunately this only
affects users who have set the 'unix_sock_dir' config parameter
in /etc/libvirt/libvirtd.conf, which is pretty rare/unusual.

Signed-off-by: eater <=@eater.me>

Exception made for the psuedonym above since patch is considered
trivial & thus non-copyrightable material.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>