Add UDP test scenario

Update test_healthmonitor_traffic & test_basic_traffic tests
to support UDP traffic in test_traffic_ops
Add simple UDP test in test_ipv6_traffic_ops

Add a UDP test server, merged with the existing HTTP test server.

Change-Id: I1e497b75672753ed0e7acf482bc0e4a6138d3437
diff --git a/octavia_tempest_plugin/common/constants.py b/octavia_tempest_plugin/common/constants.py
index e31c1a5..0424cc5 100644
--- a/octavia_tempest_plugin/common/constants.py
+++ b/octavia_tempest_plugin/common/constants.py
@@ -138,6 +138,7 @@
 HEALTH_MONITOR_HTTP = 'HTTP'
 HEALTH_MONITOR_HTTPS = 'HTTPS'
 HEALTH_MONITOR_TLS_HELLO = 'TLS-HELLO'
+HEALTH_MONITOR_UDP_CONNECT = 'UDP-CONNECT'
 
 # Session Persistence
 TYPE = 'type'