Don't log Self-Managed calls that ended before complete

We used to log all handovers that did not end in
failure, including handovers that were still in
progress when the original call ended. We now only
log handovers that completed successfully.

Bug: 63096530
Test: Manual, procedure in Bug report, Telecom unit tests
Change-Id: I035f38e23ab1270f7d659e30268956d9b6785b5a