public synchronized void addPending(String container, int moduleSequence, ModuleDescriptor.Key key) {
			pending.add(new ContainerModuleKey(container, moduleSequence, key));
		}
Indicate that a reply is expected for a module deployment request
to the container for the module indicated by the module descriptor key.

@param container       container name
@param moduleSequence  module sequence
@param key             module descriptor key
spring-xd-dirt/src/main/java/org/springframework/xd/dirt/server/admin/deployment/zk/ModuleDeploymentWriter.java