Refactor CountryDetectorService

Clean-up the test to use Mockito instead of the deprecated
AndroidTestCase, also getting rid of 1.5s of Thread.sleep.
No logic change.

Bug: 141626568
Test: atest CountryDetectorServiceTest
Change-Id: Ic0782b1ffcd1dcb30b9f1d91b37521d1f9887f03
diff --git a/services/tests/servicestests/Android.bp b/services/tests/servicestests/Android.bp
index 3910993..015e574f2 100644
--- a/services/tests/servicestests/Android.bp
+++ b/services/tests/servicestests/Android.bp
@@ -28,6 +28,7 @@
         "services.net",
         "services.usage",
         "guava",
+        "androidx.test.core",
         "androidx.test.runner",
         "androidx.test.rules",
         "mockito-target-minus-junit4",