fix scenario: ipv6 but ha-bindiface not available in relation

hooks/hacluster.py

@@ -90,6 +90,10 @@ def get_network_address(iface):
 
 
 def get_ipv6_network_address(iface):
+    # Behave in same way as ipv4 get_network_address() above if iface is None.
+    if not iface:
+        return None
+
     try:
         ipv6_addr = utils.get_ipv6_addr(iface=iface)[0]
         all_addrs = netifaces.ifaddresses(iface)

hooks/hooks.py

@@ -75,8 +75,7 @@ def get_corosync_conf():
             bindiface = relation_get('corosync_bindiface',
                                      unit, relid)
             conf = {
-                'corosync_bindnetaddr':
-                bindnetaddr(bindiface),
+                'corosync_bindnetaddr': bindnetaddr(bindiface),
                 'corosync_mcastport': relation_get('corosync_mcastport',
                                                    unit, relid),
                 'corosync_mcastaddr': config('corosync_mcastaddr'),