This patch fixes the `TestRunAttachTermination` flaky runs.
It seems like we weren't halting on the `waitFunc` so if the
process was fast enough to setup the signal handler and execute
`waitExitOrRemoved`. We now instead wait for the `killCh` channel
to close inside the mocked `waitFunc`.
Signed-off-by: Alano Terblanche <18033717+Benehiko@users.noreply.github.com>