Fix for OPENDJ-846, Intermittent Replication failure.
The issue was triggered by the mix of AssuredReplication and bad network conditions, which resulted in a deadlock between 2 RS, as both were blocked on writing to the TCP socket and not reading (because waiting on the write lock).
The solution (more of a workaround) is to have another thread for sending data to the socket and have the reader and writer posting data to send to a queue that this new thread is polling.
There are still potential deadlocks but they will occur much later, if the sendQueue gets full.  The code needs more work post 2.6 to be fully non blocking, but the changes are enough for now to resolve the customer deadlock case.