Merge "Change the doc to reflect the default status of preferential network service" into sc-dev am: c03fb15e am: c45b4a0a am: 90f66785

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

Change-Id: I58942093ef78a229dc1bdbd8e05b6392eeea18be