Merge "Change the doc to reflect the default status of preferential network...

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

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

Change-Id: Id3afae60a414750b735d171cc679122418465f99