Update dependencies to support Groovy

[lourot]

Without this fix we get:

2021-01-12 17:58:55 [ERROR]     Traceback (most recent call last):
2021-01-12 17:58:55 [ERROR]       File "/var/lib/juju/agents/unit-arista-virt-test-fixture-0/charm/hooks/install", line 142, in <module>
2021-01-12 17:58:55 [ERROR]         main(CharmAristaVirtTestFixture)
2021-01-12 17:58:55 [ERROR]       File "lib/ops/main.py", line 324, in main
2021-01-12 17:58:55 [ERROR]         _emit_charm_event(charm, dispatcher.event_name)
2021-01-12 17:58:55 [ERROR]       File "lib/ops/main.py", line 130, in _emit_charm_event
2021-01-12 17:58:55 [ERROR]         event_to_emit.emit(*args, **kwargs)
2021-01-12 17:58:55 [ERROR]       File "lib/ops/framework.py", line 211, in emit
2021-01-12 17:58:55 [ERROR]         framework._emit(event)
2021-01-12 17:58:55 [ERROR]       File "lib/ops/framework.py", line 729, in _emit
2021-01-12 17:58:55 [ERROR]         self._reemit(event_path)
2021-01-12 17:58:55 [ERROR]       File "lib/ops/framework.py", line 772, in _reemit
2021-01-12 17:58:55 [ERROR]         custom_handler(event)
2021-01-12 17:58:55 [ERROR]       File "/var/lib/juju/agents/unit-arista-virt-test-fixture-0/charm/hooks/install", line 55, in on_install
2021-01-12 17:58:55 [ERROR]         if CompareHostReleases(ubuntu_series) < 'bionic':
2021-01-12 17:58:55 [ERROR]       File "lib/charmhelpers/core/strutils.py", line 94, in __init__
2021-01-12 17:58:55 [ERROR]         raise KeyError("Item '{}' is not in list '{}'"
2021-01-12 17:58:55 [ERROR]     KeyError: "Item 'groovy' is not in list '('lucid', 'maverick', 'natty', 'oneiric', 'precise', 'quantal', 'raring', 'saucy', 'trusty', 'utopic', 'vivid', 'wily', 'xenial', 'yakkety', 'zesty', 'artful', 'bionic', 'cosmic', 'disco', 'eoan', 'focal')'"
2021-01-12 17:58:55 [ERROR]     2021-01-12 17:58:53 ERROR juju.worker.uniter.operation runhook.go:136 hook "install" (via explicit, bespoke hook script) failed: exit status 1
2021-01-12 17:58:55 [ERROR]     2021-01-12 17:58:53 INFO juju.worker.uniter resolver.go:143 awaiting error resolution for "install" hook

https://openstack-ci-reports.ubuntu.com/artifacts/test_charm_pipeline_func_full/openstack/charm-neutron-api-plugin-arista/761538/2/7734/consoleText.test_charm_func_full_10786.txt

Sorry for the hacks in the build script but this is a test fixture and I think moving to using charmcraft can wait a bit more. Validated locally.