fix(uat): ease race between MQTT connect and agent reconnect

uat/mqtt-client-control/src/main/java/com/aws/greengrass/testing/mqtt/client/control/implementation/EngineControlImpl.java

@@ -178,9 +178,10 @@ public void onDiscoveryAgent(@NonNull String agentId, @NonNull String address, i
             } else {
                 logger.atInfo().log("Agent {} relocated to {}:{}", agentId, address, port);
                 agents.remove(agentId);
-                stopAgent(agentId, agentControl, false);
-                // recursion
+                // recursion just to add new relocated agent
                 onDiscoveryAgent(agentId, address, port);
+                // stop can take long time (about 2 seconds)
+                stopAgent(agentId, agentControl, false);
             }
         }
     }

uat/testing-features/src/main/java/com/aws/greengrass/steps/MqttControlSteps.java

@@ -759,9 +759,6 @@ public void connect(String clientDeviceId, String componentId, String brokerId,
         }
 
 
-        // get agent control by componentId
-        AgentControl agentControl = getAgentControl(componentId);
-
         // request for new MQTT connection
         final String clientDeviceThingName = getClientDeviceThingName(clientDeviceId);
 
@@ -777,6 +774,9 @@ public void connect(String clientDeviceId, String componentId, String brokerId,
                      brokerId, host, port, clientDeviceThingName, componentId, mqttVersion);
             MqttConnectRequest request = buildMqttConnectRequest(
                     clientDeviceThingName, caList, host, port, version);
+            // get agent control by componentId as late as possible to reduce race probability
+            AgentControl agentControl = getAgentControl(componentId);
+
             try {
                 ConnectionControl connectionControl
                         = agentControl.createMqttConnection(request, connectionEvents);