Notify all data disconnected on DCT initialized

This ensures data disconnected listeners do not miss the notification on
a phone process crash. Once a data connection is established, it will
then notify listeners that data is connected again.

Test: atest DcTrackerTest
Bug: 186507152
Change-Id: I68618927cf40217f05136614c847c1e545008ec9
Merged-In: I68618927cf40217f05136614c847c1e545008ec9