Fix up test topHandler03 by ignoring unhelpful shell output

Shells! Grrrr. Some shells print out a message if your program terminates with
a signal. In the case of topHandler03 which deliberately exits with signal 15
SIGTERM, some shells were printing "Terminated" to stdout.

Why the testsuite driver goes via a shell I do not know (it also messes up the
exit codes for signals).