Fix IP generation for automatic bridge device

[methadata]

Previously, the IP was generated in a network that would not encompass container's original IP: It only worked for /16 networks :)

To illustrate, with the previous incarnation: 192.168.123.2/24 would become 193.168.123.2/23, not very useful because the latter does not include the former. OTOH with the fix 192.168.123.2/24 would become 192.168.122.2/23 which does actually include the former IP.

[LLParse]

We don't use container network for VMs anymore. Closing.