Use default LogEvent copy constructor

This prevents subtle bugs from being introduced when more member
variables, such as annotations, are added to LogEvent.

Test: m statsd
Test: atest statsd_test
Test: atest GtsStatsdHostTestCases
Bug: 156312371
Change-Id: Ibb5366e8658d6c99e5730b4bc301190655bbd245
2 files changed