Comment 9 for bug 1805322

The issue got fixed on commit 518ae9a0 [1].

There were two issues involved:
1) As mentioned by James on comments #1 and #2, apt_install was called no matter the value of action-managed-upgrade. apt_install determined which packages (and versions) to install by checking "openstack-origin" (the mentioned commit now installs available updates on the current mirrors).

2) A non-stepped update was tried. Xenial's "distro" packages are Ocata. If an update to Pike, then Queens, would have happened, the upgrade would have worked (however, action-managed-upgrade should have worked and [1] fixes it).

1. https://opendev.org/openstack/charm-neutron-api/commit/518ae9a0