Fix potential mismatched caller information

This fixes a bug where caller information returned for a call
waiting would be mistakenedly applied to an existing call by
ensuring that the returned contact information is only assigned
to the call that initiated the lookup.

1) Active call A is in progress
2) Incoming call B (call waiting)
3) Contact info lookup is initiated for call B
4) Call B is rejected
5) Contact info is returned
6) UI for call A is updated with the returned info

Bug: 24591055
Change-Id: I41e0741d8bc01a2fe98d77cb080d1df455b1e5df