Fix externaldns and faliover k8s tests.

Reduce load when retrying by adding interval parameter to retry
helper.
Implement controller_name caching that will reduce load on salt
and will allow to renew controller if it needed (like for
failover test)

Change-Id: I4172f9cac1f1aeac8c356f338d50299f31ed0b66
diff --git a/tcp_tests/tests/system/test_failover_k8s.py b/tcp_tests/tests/system/test_failover_k8s.py
index b872c36..7382bb9 100644
--- a/tcp_tests/tests/system/test_failover_k8s.py
+++ b/tcp_tests/tests/system/test_failover_k8s.py
@@ -71,5 +71,7 @@
             host=config.salt.salt_master_host, raise_on_err=False)['stdout'])
         assert "apiVersion" in curl_output
 
+        k8s_actions.renew_controller(controller_node_name=new_minion_vip)
+
         show_step(8)
-        k8s_actions.run_conformance(node_name=new_minion_vip)
+        k8s_actions.start_conformance_inside_pod()