server hangs with threadpool,protocol compression and client pipelining

to reproduce

mysql-test-run.pl compress --mysqld=--thread-handling=pool-of-threads --ps-protocol

The C/C client uses pipelining for prepared statements, happens packs 2 protocol packets COM_STMT_RESET+COM_STMT_EXECUTE into single compressed packet.

After executing the COM_STMT_RESET threadpool believes there is no more data from client (it does not check if any unread data is present in THD::NET), so it decides to wait for more client input, while client is waiting for the results of COM_STMT_EXECUTE.