Chunk server: implement max. wait time for incoming request by returning "server busy" if the request max. wait time exceeds buffer io queue(s) average wait time. For write requests (especially write append that use connection pooling) limit max payload discard to chunkServer.clientSM.maxReqSizeDiscard (default 256K) bytes. Replace KfsOp::Show() with more efficient version that doesn't require memory allocation, and std::stringstream construction.
Qfs client lib: set request max wait time for all requests on the client side equal to request timeout.
The primary intetion of these change is to reduce request latency due to "failing" drives.