Check if anyone could possibly provide service.

If no service is present that could satisfy a given ServiceWatcher,
then return false.  For example, on devices were there is no Geocoder
service implementation, we need to avoid claiming that the API is
supported.

Test: booted
Bug: 30837973
Change-Id: Ib0834cf1a12623733f8b472dc3da7b3e2adc4515