Disabling the batchSender if there is an img error

If the img request errors out, this will cause the batchsender to shut down. It will stop making images, but still purge the events it receives to avoid a memory leak.

This is a short term fix for if the beacon endpoint goes down. Without this fix, the image requests block and take a long time to resolve, really slowing down ALM. 

The long term fix for this problem is here: https://rally1.rallydev.com/#/7427420584d/detail/portfolioitem/feature/22669461677