Fixed unnecessary virtual declarations in classes without inheritance (only detected by the SLC5 compiler).

Removed interface classes DiskReadTaskInterface, DiskWriteTaskInterface, DiskThreadPoolInterface

Otherwise, there was a race condition between the control thread and the worker threads.
Now, the log context of the worker thread is passed and used by popAndRequestMore.

and DiskReadThreadPool

Renamed member variables to canonycal m_
Renamed TaskInjector->end to TaskInjector->finish() to match other threads conventions.
Fixed missing finish() in RecallTaskInjectorTest
Added missing finish() call in TapeReadTSingleThread.

setTaskInjector, popAndRequestMore have been created and m_maxBytesReq,m_maxFilesReq have been added to be able to call TaskInjector::requestInjection

DiskReadThreadPool::WorkerThread::run has been changed consequently

DiskReadTask -> DiskReadTaskInterface, DiskReadFileTask -> DiskReadTask, same thing for the write side. Changed the includes files accordingly

and refactor a bit of code into the interface

We are now using the matching files and classes frpm castor/tape/threading