Remove useless (or undocumented) sleep() calls that were slowing down Python scipy build

This removes useless (or undocumented) sleep() calls.  Calling read() on a pipe will block until data is available, so there is no reason to sleep().

There is one more sleep() that I marked with a comment in `run_cmd_qa`.  But because the function tries to emulate human input, the sleep() might be needed there if the program we interact with expects a delay (quite unlikely).