Don't keep re-trying the same bake (spinnaker#997)

* fix(baking): Don't keep re-trying the same bake

* fix(baking): re-work ImageHandler to use a diff

* fix(baking): re-work to use DiffFingerprintRepository instead of a new thing

fix(resource): tweak thread model, add more debug (spinnaker#1001)

Add additional debugging logging.

Change the threading model of an async call to see if it works around
issue spinnaker#951.

fix(tests): remove redundant test code

fix(bake): nice string rather than a garbage string (spinnaker#993)

chore(bake): add a metric to alert on for when we bake too much (spin…

…naker#992)

fix(bake): locate baseami (spinnaker#990)

fix(baking): Fetch base AMI version from latest base image (spinnaker…

…#988)

Previously I was trying to compare the base AMI version from the current application AMI to the base AMI _name_ from `BaseImageCache` resulting in infinite rebaking.

fix(actuator): add coroutine id to help debug (spinnaker#985)

Create an ad-hoc coroutine id to help make gather related log messages.
This is a temporary change to make it easier to go through the log
messages for debugging spinnaker#951.

fix(artifacts): don't keep marking as deployed over and over (spinnak…

…er#982)

fix(summary): add artifact reference (spinnaker#981)