Use correct default subscription id to get default network template.

- when launching the app info page and no network template is defined in
the launch arguments, use the correct default data subscription id to
check whether mobile network template should be used or not.

Change-Id: If9341abf3416c775a2b7407c1d6d0b33f4aad67f
Fixes: 120098637
Test: make RunSettingsRoboTests