Refactored INetworkPolicyListener callbacks.

Methods onRestrictBackgroundWhitelistChanged() and
onRestrictBackgroundBlacklistChanged() were replaced by a more generic
onUidPoliciesChanged().

Test: m javac-check RUN_ERROR_PRONE=true
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.NetworkPolicyManagerServiceTest" -w "com.android.frameworks.servicestests/android.support.test.runner.AndroidJUnitRunner"

BUG: 28791717
Change-Id: I18b2ee4af06802e0d23822b153d1be9b429d5811