test: fix test-net-listen-fd0 for pipes

In the case of a pipe'd input, i.e. from the CI the fd will be a PIPE
and when listen() is called it will return ENOTSOCK instead of EINVAL.
test: make abort-fatal-error more robust

It's saner to check exit codes or signals to determine if the process
actually aborted. On OSX and Linux the exit code is 134, on SunOS it
propagates the SIGABRT signal