Add src/README.md placeholder to prevent inheritence of the
base layer's readme file in the built charm.
Use the official charms.openstack repo in test-requirements.txt.
Use official designate-bind charm location in the Amulet tests.
Remove upload-and-publish so as not to encourage out-of-band
pushing and publishing. That is handled by CI.
Fix a test filename typo.
Add tests readme.
Update tox.ini for Amulet environment variables.
Update metadata.yaml, removing EOL release and adding tags.
Fix unit tests
Change-Id: If842a5409c2d284bc118d70d6e8caba7cb6205c3
Nicolas Bock