Update Pdfork.OtherUserIfRootForked for actual FreeBSD behaviour (#53)
Update Pdfork.OtherUserIfRootForked for actual FreeBSD behaviour (#53)

FreeBSD does not currently allow sending signals via pdkill to a process
that is running with a different UID (unless we are root).
This test is currently failing for me on FreeBSD 12.2 and 13. We can still
send a SIGKILL via close(), but pdkill() returns EBADF.
google/capsicum-test,google/capsicum-test,google/capsicum-test,google/capsicum-test