Moved data connection response into system api.

This is a preliminary step for IWLAN refactoring, where data response
will be one of the parameter in data service callback.

Test: Telephony sanity tests
bug: 64132030
Merged-In: Ie3cfc59c98bdd362a89207dc517f92619fa2278a
Change-Id: Ie3cfc59c98bdd362a89207dc517f92619fa2278a
(cherry picked from commit 3f8bd3dd)