Instead of asserting that the peer responds successfully, this API
allows for the peer to die/crash/whatever happens on the other side
while handling a synchronous request.
This will be useful when using process separation to parse untrusted
data from the web.
The PIDs were used for sharing shbufs between processes, but now that
we have migrated to file descriptor passing, we no longer need to know
the PID of the other side.
