Integration tests for COS integration for OpenStack

[cbartz]

Overview

Follow-up to #266 to provide integration tests running on the openstack cloud.

An integration test related to COS and repo policy compliance will be provided in a follow-up PR.

The OpenStack tests are not yet included in the CI, as there is another PR working on getting Openstack to work on the CI: #269

This PR does also refactor the helper modules. Due to parallel development on the openstack integration tests, the other integration tests have not been tested to see if they still work and this will need to be investigated in a follow-up.

The openstack applicable tests are marked now with an openstack pytest mark.

This PR also fixes/adds:

• Private ssh keys have now correct permission and are owned by ubuntu user (to avoid ssh permission warning)
• RunnerStop metric is also issued on abnormal termination
• More context on pull metrics file errors (add a warning log that the metrics file size could not be determined)

Rationale

Add integration tests to ensure proper functioning.

Juju Events Changes

n/a

Module Changes

A separate package has been introduced and the helper modules have been placed there. There is a module for LXD and Openstack that contains cloud specific code. An interface InstanceHelper has been defined which is implemented for both clouds. It is required to handle cloud specific helper code as run_in_instance' or ensure_one_runner' or `get_runner_name'.

The test_charm_metrics_{success,failure} tests have been adapted and the openstack applicable tests are marked with an openstack mark.

Beyond that:

• openstack_manager: Now writes ssh key with correct permission and ubuntu user
• openstack_userdata.j2: Fix case where write_post_metrics function is not called on non-zero exit code of previous command

Library Changes

Checklist

• The charm style guide was applied
• The contributing guide was applied
• The changes are compliant with ISD054 - Managing Charm Complexity
• The documentation is generated using src-docs
• The documentation for charmhub is updated.
• The PR is tagged with appropriate label (urgent, trivial, complex)

[yhaliaw]

Some comments.

[yanksyoon]

Reviewed until helpers/lxd.py, cool stuffs!

[yhaliaw]

@yanksyoon I think you can merge this, when you approve it.

[yanksyoon]

LGTM! Thanks for the changes!