apmanager: Fix service_unittest.cc `sleep` call.

service_unittest.cc uses libchromeos::ProcessImpl to start a `sleep`
process, but ProcessImpl doesn't search PATH so the process was failing.
The test still succeeded in most cases because the failed process
existed as a zombie.

BUG=chromium:438274
TEST=Ran unittest.

Change-Id: I5834050dc13890545cf9124c76799cf6f1f02446
Reviewed-on: https://chromium-review.googlesource.com/232710
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Tested-by: David Pursell <dpursell@chromium.org>
Commit-Queue: David Pursell <dpursell@chromium.org>
1 file changed