test: fix perf metrics uploader crash
test: fix perf metrics uploader crash

We were accidentally looking at time_ended instead of time_started
(time_ended is not populated until after the uploader returns...).

This wasn't caught in local tests as the jobs tested were all completed
jobs and obviously they had the time_ended field.

Change-Id: I07a26dfd218aedc10e909535c623a2ae37f87821
google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto