Minor Worker application related fixes.

Make sure the workers reference the correct wait handle and are in the RDS security group.

cloudformation_templates/edx-reference-architecture.json

@@ -3974,6 +3974,9 @@
               "Ref":"EdxappServerSecurityGroup"
             },
             "EC2SecurityGroupId":{
+              "Ref":"WorkerServerSecurityGroup"
+            },
+            "EC2SecurityGroupId":{
               "Ref":"XqueueServerSecurityGroup"
             }
           }
@@ -4103,7 +4106,7 @@
                 "{\n",
                 "  cfn-signal -e 1 -r \"$1\" '",
                 {
-                  "Ref":"EdxServerWaitHandle"
+                  "Ref":"WorkerServerWaitHandle"
                 },
                 "'\n",
                 "  exit 1\n",
@@ -4142,7 +4145,7 @@
                 "# If all went well, signal success\n",
                 "cfn-signal -e $? -r 'Edx Server configuration' '",
                 {
-                  "Ref":"EdxServerWaitHandle"
+                  "Ref":"WorkerServerWaitHandle"
                 },
                 "'\n"
               ]