Ensure standby bucket of an unused app gets treated correctly.

An unused app should be in NEVER bucket but without this change,
when we calculate the standby bucket of an app that was never used,
it could end up in RESTRICTED bucket.

Bug: 206518483
Test: atest tests/tests/app.usage/src/android/app/usage/cts/UsageStatsTest.java
Change-Id: I839041b7aedc87923879ca872c570c35c39b85a5