Mobile data in quick setting still work if default data not set

Even if default data subscription is not set, we'll make "Mobile data"
toggle in quick setting work. It will find an active subscription, turn
on its mobile data, which implicitly makes it default data sub.

Bug: 132063538
Test: robo test and manual

Change-Id: I05263ca6e7e0f9171c6d34c7b628553b9ec506ab