reduce the pass-count from 100 to 50; this is more than enough to prove
that the test is working, and helps reduce the ever-increasing time it's
taking to run the entire test suite.
get started before trying to ptrace(ATTACH). Otherwise, the traced
process doesn't seem to resume properly upon ptrace(DETACH) and on the
next pass the ptrace(ATTACH) just hangs forever, causing the test to
time-out.
XXX The failure-to-resume-properly might actually be a kernel bug that
we need to follow up on. But for now, let's make the test work as
intended.