Fix randomly showing anomaly icon

Sometimes PowerGaugePreference will show anomaly icon when they
shouldn't. I think it is because PreferenceViewHolder has cache
about the previous data.

This cl fixes it by setting compound drawable as 0 when
showAnomalyIcon is false.

Bug: 36924669
Test: RunSettingsRoboTests
Change-Id: I5ea0dc307aafcce386c84963e618d1213de5ec19