oeqa/runtime: make minidebuginfo test work with coreutils

The test was failing with core-image-full-cmdline which uses sleep from coreutils instead of sleep from busybox.

Signed-off-by: Etienne Cordonnier <ecordonnier@snap.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 8497edf0)
Signed-off-by: Steve Sakoman <steve@sakoman.com>