Fixed dangling DC controller

Instead of creating a DcController everytime, we reuse
the existing DcController.

Test: Manually tested with APM + wifi calling on. Killed the data service and saw the existing DCC being re-used and working correctly.
Bug: 176458078
Merged-In: I6a74fcaf60f66e49a389ae9840a925dc789940f1
Change-Id: I861de7162d2311e494e79215f60a92ac89279622