Isolate NetworkStateTracker creation, test.

Change ConnectivityService to use a factory when creating
NetworkStateTrackers, which gives us a good place to inject mocks
for testing.  Add initial tests to verify that network routes are
added and removed as networks changed.

Change-Id: I11cbc61a84c2ed4afa2670036295b1494eab26e1
diff --git a/services/tests/servicestests/Android.mk b/services/tests/servicestests/Android.mk
index 295f324..81a2c14 100644
--- a/services/tests/servicestests/Android.mk
+++ b/services/tests/servicestests/Android.mk
@@ -9,7 +9,8 @@
 
 LOCAL_STATIC_JAVA_LIBRARIES := \
     easymocklib \
-    guava
+    guava \
+    littlemock
 
 LOCAL_JAVA_LIBRARIES := android.test.runner services