Refactored NetworkStatsServiceTest to use Mockito instead of EasyMock.

Test: m -j32 FrameworksServicesTests && adb install -r -g ${ANDROID_PRODUCT_OUT}/data/app/FrameworksServicesTests/FrameworksServicesTests.apk && adb shell am instrument -e class "com.android.server.net.NetworkStatsServiceTest" -w "com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner"

BUG: 30943463
Change-Id: I3fbdb0918f1d0e68f32afe07ca38d4ef217025df
2 files changed