CS-15256: Unable to associate cluster with Nexus VSM upon a retry if addCluster command fails the first time

Description:

	Putting in code to clean up stale VSM records in case
	addCluster fails to communicate with the vCenter server.

server/src/com/cloud/resource/ResourceManagerImpl.java

@@ -576,6 +576,7 @@ public class ResourceManagerImpl implements ResourceManager, ResourceService, Ma
             if (!success) {
                 _clusterDetailsDao.deleteDetails(clusterId);
                 _clusterDao.remove(clusterId);
+                _clusterVSMDao.removeByClusterId(clusterId);
             }
         }
     }