Add another version of the simple ping test, this time written as a
shell script and using rump_server, rump.ifconfig and rump.ping.

XXX: uses rump_allserver for now, though, since i noticed a problem
where the rump kernel syscall vector does not get updated for
dlopen()'d libraries (and hence if you dlopen librumpnet.so, socket()
still gives ENOSYS).  Me be fixink it later.

(pooka)