The current implementations use of a specific interface to build
FQDN from has the undesired side effect of the ``nova-compute`` and
``neutron-openvswitch`` charms ending up with using different
hostnames in some situations. It may also lead to use of a
identifier that is mutable throughout the lifetime of a deployment.
Allows to configure a dedicated migration network.
This commits adds a new extra binding (migration) and
its corresponding fallback configuration flag (libvirt-
migration-network) that allows to specify a space or an
existing CIDR formatted network (if the config flag is pre-
ferred) that will be seleced as the inbound address to be used
as a the live migration target.
For the case of any openstack release >= ocata,
the live_migration_inbound_addr variable will be set
as well as the libvirt_migration_scheme (set to SSH
by default).
For older releases, the behavior remains as before,
as the only remaining option is to setup libvirt
to bind in a insecure tcp connection, so we keep it
as the current live_migration_uri.
The reason of not using an extra-binding exclusively relies
on the back-compability of the change, this needs
to be applied on existing clouds where updating
the bindings on deployed application
isn't possible due to LP: #1796653.
For fresh/new deployments, the migration extra-binding
has been defined and used with precedence over the
libvirt-migration-network variable.
Insert the hooks directory at the beginning of sys.path in order to
make it take precedence over other entries, e.g. in the face of
conflicting charmhelpers packages.
