Annotate Locations coming from mock providers

LocationManagerService now annotates incoming Location objects that
have come from mock location providers. The new isFromMockProvider()
method can be called on any Location to determine whether the
provider that supplied the Location was a mock location provider.

Bug: 6813235
Change-Id: Ib5140e93ea427f2e0b0036151047f87a02b4d23a