automation: don't create resources when deleting things Otherwise running these commands can result in resources being created. In the case of `purge-ec2-resources`, we will create resources only to delete them immediately afterwards! With this change, `purge-ec2-resources` now no-ops if no resources exist. # no-check-commit because foo_bar function name Differential Revision: https://phab.mercurial-scm.org/D6285