void undeployAllModules() {
		for (Iterator<ModuleDescriptor.Key> iterator = mapDeployedModules.keySet().iterator(); iterator.hasNext(); ) {
			ModuleDescriptor.Key key = iterator.next();
			try {
				undeployModule(key.getGroup(), key.getType().name(), key.getLabel());
			}
			catch (Exception e) {
				logger.warn("Exception while undeploying " + key, e);
			}
			iterator.remove();
		}
	}
Determine whether the provided descriptor has a tap channel as its "source", and if so return the unqualified tap
channel name. If not, return {@code null}.

@param descriptor ModuleDescriptor whose source channel is checked
@return unqualified tap channel name or {@code null}
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/server/container/DeploymentListener.java