Ensure that health check controller is unbound correctly

Explicitly call into the health check controller if there are
no more packages to check. This is due to the fact that
the ExplicitHealthCheckController will unbind itself in this
case. If this call is not made, the controller will continue
running in the foreground and will not be killed by lmkd.

Test: atest PackageWatchdogTest
Test: check logcat to see that the service is unbound
Bug: 156323728
Change-Id: I0044d0832178ee90043d5e64e406df07ee2c36a2