EventSequenceValidator: Only record the debug log in debugging level.

The stack trace log may confuse other developers and mistakenly points
to IORap as the bug cause.

cherry-pick from ef5e1a6d

Bug: 161145462
Test: Make and check the logcat.
Merged-In: I3cb24cace060cff381ab3c5770ff6c1c948a2d89
Change-Id: I3cb24cace060cff381ab3c5770ff6c1c948a2d89