Pass result list in return value, not in param

Address comment in ag/10101436. Passing the result list in
listEventsAsProto() through return value not through adding to existing
param.

Bug: 146086778
Test: $ incident_report 3049, then compare the content with "dumpsys
      connmetrics"

Change-Id: Icf0c11650883172d6ffeecdf7f898b3c6fb85b27
3 files changed