Add ha_nodes option to murano-repository

NOTE:
   This patch is intended only for 4.1 branch
   due to changes in murano repositories structure.

   This patch is required to have murano-repository HA mode working.

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.

Config 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 opened 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.

Based on: https://review.openstack.org/#/c/83146/3

Implements: blueprint murano-repository-ha

Change-Id: I4ff3005422e1360f57dd3f5e57a888dff6a19dd1
Merge "Add ha_nodes option to murano-repository" into stable/4.1