Disable docker-cleanup job when 'testing: true'.

If a container is in a crash loop, when the `docker-cleanup` script runs, it has
a good chance of being removed.

When doing tests, its not uncommon to be in a crash loop scenario while trying
to resolve problems, and it is undesirable to have the container removed out
from under you.

This is particularly problematic when the container is large and/or the network
between you and the registry is not optimal, as one has to repeatedly
re-download the container.
5 jobs for testing_disable_cleanup in 0 seconds (queued for 111 minutes and 57 seconds)