Fix live events on exit bug

This should ensure we capture live events on exit correctly.

Test Plan:
 - clear your dev logs on your canvas
 - start canvas, make some live events calls
 - stop canvas, grep your dev logs for live events output
  - should not see anything that is an error

Change-Id: I5faf89eb1b3d288287978680195a3fe3c0c35eb5
Reviewed-on: https://gerrit.instructure.com/212483
Tested-by: Jenkins
Reviewed-by: Weston Dransfield <wdransfield@instructure.com>
QA-Review: Weston Dransfield <wdransfield@instructure.com>
Product-Review: Marc Phillips <mphillips@instructure.com>

gems/live_events/lib/live_events/async_worker.rb

@@ -95,7 +95,7 @@ module LiveEvents
         begin
           # r will be nil on first pass
           records = [r].compact
-          total_bytes = r&.fetch(:total_bytes) || 0
+          total_bytes = (r.is_a?(Hash) && r[:total_bytes]) || 0
           while @queue.size > 0 && total_bytes < MAX_BYTE_THRESHOLD
             r = @queue.pop
             break if r == :stop

gems/live_events/spec/live_events/async_worker_spec.rb

@@ -20,7 +20,7 @@ require 'spec_helper'
 
 describe LiveEvents::AsyncWorker do
   let(:put_records_return) { [] }
-  let(:stream_client) { double(stream_name: stream_name) }
+  let(:stream_client) { double(stream_name: stream_name, put_records: OpenStruct.new(records: [], error_code: nil, error_message: nil)) }
   let(:stream_name) { 'stream_name_x' }
   let(:event_name) { 'event_name' }
   let(:event) do
@@ -139,6 +139,7 @@ describe LiveEvents::AsyncWorker do
     it "should drain the queue" do
       @worker.push(event, partition_key)
       expect(@worker).to receive(:at_exit).and_yield
+      expect(LiveEvents.logger).not_to receive(:error)
       @worker.start!
       @worker.send(:at_exit)
     end