Fix the app ops settings tests by adding FLAG_ACTIVITY_NEW_TASK to Intents.

Test: make -j32 SettingsUnitTests && adb install -r out/target/product/marlin/data/app/SettingsUnitTests/SettingsUnitTests.apk && adb shell am instrument -w -e class com.android.settings.applications.ExternalSourcesSettingsTest com.android.settings.tests.unit/android.support.test.runner.AndroidJUnitRunner
Change-Id: I187d68e6b214d975df0fe2a3d5dc88cadec35fa3