Use CONSUL_TLS_SERVER_NAME for watches if ssl is enabled in agent

While setup consul watches make sure that we are establishing connection to the correct CONSUL_TLS_SERVER_NAME if agent is configured to use SSL (CONSUL_HTTP_SSL=true)

This is initial attempt to fix hashicorp#4718

Extended debugging capabilities of the agent.

agent/agent.go

@@ -750,7 +750,7 @@ func (a *Agent) reloadWatches(cfg *config.RuntimeConfig) error {
 
 			addr := config.Address
 			if config.Scheme == "https" {
-				addr = "https://" + addr
+				addr = "https://" + config.TLSConfig.Address
 			}
 
 			if err := wp.RunWithConfig(addr, config); err != nil {