Capture event log

This test, and the code it is testing, makes use of the event log -
looking for specific info in it, and writing to it.

Make sure we capture the event log during runs of the test so that we
have some chance of diagnosing falures.

Bug: 239817928
Test: N/A
Change-Id: I610c7ddd67381d04c35fd42343e21098c150beb5