Use mockito-extended in FrameworksNetTests

This is necessary to mock classes like BatteryStatsManager, which cannot
be used without signature permissions, and to merge the test with other
test suites that use mockito extended.

Bug: 187935317
Test: atest FrameworksNetTests
Change-Id: I5dba65d806c5d06b3ff8f633846edb911a7a44ec
diff --git a/tests/unit/AndroidManifest.xml b/tests/unit/AndroidManifest.xml
index d08b2f8..18653dc 100644
--- a/tests/unit/AndroidManifest.xml
+++ b/tests/unit/AndroidManifest.xml
@@ -50,7 +50,8 @@
     <uses-permission android:name="android.permission.NETWORK_STATS_PROVIDER" />
     <uses-permission android:name="android.permission.CONTROL_OEM_PAID_NETWORK_PREFERENCE" />
 
-    <application>
+    <!-- Debuggable is necessary for mockito extended -->
+    <application android:debuggable="true">
         <uses-library android:name="android.test.runner" />
         <uses-library android:name="android.net.ipsec.ike" />
     </application>