Fix self-test for JitterVerification test case

This CL is to fix a bug caused by a recent change in JitterVerification.
The bug triggers a failure in JitterVerificationTest, which affects more devices
than JitterVerification.

Related bugs:
  * b/24367328
  * b/24373707

Change-Id: Ia68a00724e61759dd11b7ab067071f58462fcb01