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 am: 702f3250

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

Change-Id: I14aa7500e7ef40c8fe6705875a56f51780323a79