Before adding a (unit-name, address) tuple to the list of peers
for a particular address type, ensure that the unit has actually
presented data for the requested address type.
This avoids 'None' values being written to the haproxy configuration
files during initial deployment and scale back of units.
Change-Id: Ia10e1454791d92b9ca6233425b4a6ea89642def0
Closes-Bug: 1849901
set_address: New method for specifying units address for net-splits
deployments
send_all: Send setting to all peers
retrieve_local: Retrieve key from local db
retrieve_remote: Retrieve key from peers
Fix name of interface.yaml (should not be plural)
Fix tox targetss and drop charm-tools from requirements
Change-Id: I4b0b952c3490cb7c0a877cd827333d69e81ebdab
James Page