This commit adds messages such as the following:

{
   "severity":"INFO",
   "time":"2018-07-11T20:43:04.505Z",
   "pid":53975,
   "class":"Gitlab::Geo::LogCursor::Daemon",
   "message":"Skipped event",
   "log_event_id":1,
   "event_id":1,
   "event_type":"Geo::RepositoryUpdatedEvent",
   "project_id":1,
   "cursor_delay_s":0.077
}

This will help diagnose whether the cursor is actually skipping events.