Add ha_nodes option to murano-repository

This patch adds support for 'ha_nodes' option
of Murano Repository service. This
options should contain a string with
all controller nodes and service ports.

For example:
ha_nodes = node-1:8084, node-2:8084, node-3:8084

Port 8084 will be listened by other controllers
and any changes made will be replicated to all
other controllers.

Firewall should be opend to allow this port
to be accessed by other controllers through
the management network.

The Repository service uses Keystone's auth
tokens for authentificetion on other
controller nodes.

nodes_to_node_port_list function generates
this string from the array of controller nodes.

Change-Id: Iba68d14e9732fe8f53b869869dfc529392d88686
Implements: blueprint murano-repository-ha