The signal might get delivered to a different thread, and that thread
might not run again before the currently running thread returns and
exits. Sleep to give the other thread time to pick up the signal and
crash.

Not tested for all cases, but, optimistically:
Fixes #14063.

Change-Id: Iff58669ac6185ad91cce85e0e86f17497a3659fd
Reviewed-on: https://go-review.googlesource.com/23203
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Mikio Hara <mikioh.mikioh@gmail.com>