Make calls for geocoder one way

All calls out of system server must be oneway to prevent the system from
being blocked by external code. Geocode has been the very last interface
not to conform to this - this is now fixed.

Bug: 146677166
Test: atest GeocoderTest
Change-Id: Ib04d36a9b759f1737ebc2806e49f0bf1e53cea7c