fix podman-etcd: wrap ipv6 address in brackets

When trying to determine the node ip address we need to make sure we account for ipv6 and dualstack deployments, and accordingly wrap ipv6 in brackets so it correctly resolves. Since the node ip mapping is provided by the controller, we parse out the IP address of the node from there and use a helper function for building URLs with ports to correctly use brackets for ipv6 ip addresses.

Signed-off-by: ehila <ehila@redhat.com>