Adjust the condition for scanning in MRService

This CL allows foreground services to scan media route providers.

Android 12 restricts starting of FGS and doing this
enables apps to response while in the background.

Instead, the media router service unbinds from the provider services
when the device is not interactive.

Bug: 179160443
Test: manually && atest MediaRouterManagerTest
Change-Id: Ie3712e9d2cba1f801975ea49e6f48a287b3c003e