charm does not properly remove libvirt default network

[Edward Hope-Morley]

the nova-compute charm has some code added in [1] which does a net-destroy on the default network but does not undefine it so on reboot it reappears but the charm does not re-run net-destroy. Since this network can conflict with Openstack and anything else that happens to use the same subnet, we should actually undefine it so that it does not re-appear.

[1] https://github.com/openstack/charm-nova-compute/commit/b533a3fbfb96bd5939b3e790f67964ce3ba8f7fd

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/613601

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/613601
Committed: https://git.openstack.org/cgit/openstack/charm-nova-compute/commit/?id=6c8d3b47fc373a1fdc3dbc0bb6edd61fcda6f49c
Submitter: Zuul
Branch: master

commit 6c8d3b47fc373a1fdc3dbc0bb6edd61fcda6f49c
Author: Edward Hope-Morley <email address hidden>
Date: Fri Oct 26 15:32:19 2018 +0100

    Properly remove libvirt default network

    As well as destroying the network we should also undefine it
    to ensure it does not return.

    Change-Id: I57738856adb25c190357b1b23dd8a1245798cb14
    Closes-Bug: #1800160