Fix the crash while tapping "app data usage" as second user

Second user or guest is limited some mobile network access. We need to check current user
is admin or not to decide the preferece page will be found in search or not.

Bug: 133466016
Fixes: 133466016
Test: Manual test & make RunSettingsRoboTests -j56 ROBOTEST_FILTER=com.android.settings.network

Change-Id: I48d3064a8aa28ac1f2ac699b42a999b9682b1b52