Test connection on net cfg apply

When network configuration is applied, wait until we
can reach the deployment server again before exiting.

This should make us more robust against various potential delays after
changing the nature of network interfaces.

confluent_osdeploy/common/profile/scripts/confignet

@@ -567,4 +567,13 @@ if __name__ == '__main__':
     if havefirewall:
         subprocess.check_call(['systemctl', 'start', 'firewalld'])
     await_tentative()
+    maxwait = 10
+    while maxwait:
+        try:
+            tclient = apiclient.HTTPSClient(checkonly=True)
+            tclient.check_connections()
+            break
+        except Exception:
+            maxwait -= 1
+            time.sleep(1)