Get the DO client ID and key from the nearest knife.rb rather than ENV for users that have more than one DO account.
Check to see if knife bootstrap succeeded and if not delete the server and the Chef client and node, so that's it's easie to try again.
Check for DO credentials in ENV first then fallback to knife.rb. Add -y to Chef deletion commands.
Merge pull request #348 from tombh/digital-ocean-provision-error-tolerance

Use DO creds from knife.rb. Also, respond to failed knife bootstrap by deleting things.