Use CallTracker instead of mParent to get Phone in Connection

for emergency calling flow.

Currently the connection relies on the mParent to get the
 EmergencyNumberTracker, which is wrong. This can cause the HAL
 API IRadio.emergencyDial not triggered.

Test: Treehugger; IRadio.emergencyDial is triggered
Bug: 134698721
Change-Id: Ic86367d4e0c4a621b357253d5edd91c561ad53f3