OPENDJ-832 Leverage the work queue for processing requests received on the HTTP connection handler 

Code cleanup: Changed code from using AbstractOperation abstract class to using Operation interface instead.



Operation.java
Now extends Runnable.

OperationWrapper.java
Consequence of the change to Operation.java.


WorkQueue.java:
In submitOperation(), used Operation interface instead of AbstractOperation abstract class.

DirectoryServer.java:
In enqueueRequest() used Operation interface instead of AbstractOperation abstract class.
Removed CLASS_NAME constant, used this class's name in getClassName().

ParallelWorkerThread.java:
Changed instance member operation from AbstractOperation abstract class to Operation interface.

ParallelWorkQueue.java:
Changed instance member opQueue from ConcurrentLinkedQueue<AbstractOperation> to ConcurrentLinkedQueue<Operation>.
In submitOperation(), nextOperation() and retryNextOperation(), used Operation interface instead of AbstractOperation abstract class.

TraditionalWorkerThread.java
Changed instance member operation from AbstractOperation abstract class to Operation interface.
In shutDown() used Operation interface instead of AbstractOperation abstract class.

TraditionalWorkQueue.java
Changed instance member opQueue from LinkedBlockingQueue<AbstractOperation> to LinkedBlockingQueue<Operation>.
In initializeWorkQueue(), submitOperation(), nextOperation(), retryNextOperation() and applyConfigurationChange(), used Operation interface instead of AbstractOperation abstract class.
In applyConfigurationChange(), remove a duplicate condition check.



All files:
Converted java comments to javadocs.
Added @Override annotations.