Since startObservingHealth is called during boot, it is less desirable
to cause boot loops by an uncaught exception. We will fall back to
DEFAULT_OBSERVING_DURATION_MS when invalid durationMs is passed.
See b/140780361 for more details about the design decision.
Bug: 140780361
Test: atest PackageWatchdogTest
Change-Id: I2bcbecb2dc4c2448ef697001dd93aea5f50f9dbf
e0f2f3d85d