juju should use devices API on MAAS 1.8+ for addressable containers

[Dimiter Naydenov]

This came about from bug 1348663, but since it's a separate feature work I'm filing a new bug.

The "devices-api-maas" feature branch will be used.

In brief, this bug captures the work around implementing support for MAAS 1.8+ devices API in juju to let MAAS know about any containers juju creates, allocates a sticky IP address(es) for, and destroys on nodes provisioned by MAAS. Thus, MAAS knows the parent/child relationships between a node (the host) and devices on it (juju containers), as well as any allocated resources for the devices. When a node is released, MAAS takes care to release allocated addresses and other resources, without any input from juju.

On older MAAS (1.7-) we'll still use the ipaddresses API to allocate and release static IPs for containers.

When address-allocation feature flag is not enabled, the default behavior is not changed (juju creates a juju-br0 bridge device on initial boot for the containers to use and get DHCP-assigned addresses from MAAS).

[Dimiter Naydenov (dimitern)]

Michael, let's make sure we push the feature branch this forward and get it in, before 1.25 feature freeze, is possible.

[Michael Foord (mfoord)]

It's in master.