Have confignet fallback to unicast per deploycfg

In routed deployments, the scan mechanism
will not be available. Fall back to routed
access to the deploy server as indicated
by deploycfg from install time.

confluent_osdeploy/common/profile/scripts/confignet

@@ -455,6 +455,12 @@ if __name__ == '__main__':
     srvs, _ = apiclient.scan_confluents()
     doneidxs = set([])
     dc = None
+    if not srvs:  # the multicast scan failed, fallback to deploycfg cfg file
+        with open('/etc/confluent/confluent.deploycfg', 'r') as dci:
+            for cfgline in dci.read().split('\n'):
+                if cfgline.startswith('deploy_server:'):
+                    srvs = [cfgline.split()[1]]
+                    break
     for srv in srvs:
         try:
             s = socket.create_connection((srv, 443))