Make manager scans populate active scanning packages

Without populating actively scanning packages in the composite discovery
preference, self-scan route providers will not bind to system_server
when proxy routers start scanning on behalf of the self-scan provider's
router.

This change also fixes logic error in MediaRoute2ProviderServiceProxy's
binding logic.

Test: atest ProxyMediaRouter2HostSideTest MediaRouter2HostSideTest
Bug: 319604673
Change-Id: Ia079eae911f9700ef2a838d97dc7c0a24bbf6946
Flag: com.android.media.flags.enable_prevention_of_manager_scans_when_no_apps_scan