Fix taking actions without considering pending health checks

Now, we consider if we are expecting a health check result before
taking the following actions:
1. Requesting explicit health checks: Otherwise if a package has
failed health checks, we would keep requesting unnecessary health
checks from the health check service
2. Scheduling next sync: Otherwise, even after a package has passed or
failed health checks, we could keep scheduling shorter syncs than
required

Test: atest PackageWatchdogTest
Bug: 132168914
Change-Id: I817e14b6d4fa563d1c22af6ffb0461f3693a49b4