Merge pull request #403 from edx/feanil/cfn_rds_fix

Update worker server wait condition.

cloudformation_templates/edx-reference-architecture.json

@@ -4135,7 +4135,7 @@
     "WorkerServerWaitHandle":{
       "Type":"AWS::CloudFormation::WaitConditionHandle"
     },
-    "EdxServerWaitCondition":{
+    "WorkerServerWaitCondition":{
       "Type":"AWS::CloudFormation::WaitCondition",
       "DependsOn":"WorkerServer",
       "Properties":{