Merge "Change the doc to reflect the default status of preferential network service" into sc-dev am: c03fb15e am: 5dbbd226 am: 899e6449

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/15329706

Change-Id: Iefb99f3126c2ee996ebabe43251d5f2f426bd077