fix #2389: ceph wizard showing network of target node

fix #2389: ceph wizard showing network of target node

Before this patch the wizard shows the available networks for the node
one is connected to, not the actual target node where ceph is
configured. This patch changes this to access the network information of
the target node instead of the local one.
It could be that not every node in the cluster is part of the ceph
cluster (and the same network) which makes this useful.

Signed-off-by: Mira Limbeck <m.limbeck@proxmox.com>