reusing TNonblockingServer::TConnection cause dirty TSocket

TNonblockingServer reuse TNonblockingServer::TConnection when possible， and init TSocket object by
tSocket_->setSocketFD(socket);
tSocket_->setCachedAddress(addr, addrLen);
But TSocket::setCachedAddress() don't clear variable peerHost_ and peerAddress_，cause getPeerAddress() and getPeerHost() return dirty data.

Solution, clear variable peerHost_ and peerAddress_ in TSocket::setCachedAddress()