test_configure_global_cluster() is using 'has_calls',
but that does not exist in the unittest.mock library.
Use 'assert_has_calls' as eventually this will cause
a test error.
Patch out charmhelpers.osplatform.get_platform() and
charmhelpers.core.host.lsb_release() globally in the unit tests to
insulate the unit tests from the platform that the unit tests are being
run on.
Currently, the private-address for the local unit is queried using
unit_get, which can cause it to return an address from a different
binding. This patch changes it to always query from the relation.
Add the 'docs' key and point it at a Discourse topic
previously populated with the charm's README contents.
When the new charm revision is released to the Charmhub,
this Discourse-based content will be displayed there. In
the absense of the this new key, the Charmhub's default
behaviour is to display the value of the charm's
'description' key.
