Use requestSequenceId in sendTApplicationException

The incoming message's seqid is used but this sqid isn't implemented in the same way across languages. The task timeout test in TestPlainServer succeeds because java client maintains an incremental seqid starting from 1. The php client starts from a seqid of 0 and breaks.
probably a good idea to move the catch (RejectedExecutionException) into processRequest to not need to .get() the atomic, but rather use the local requestSequenceId there