Add the frequent CannotExecutePolicyError to the list of non-fatal errors trapped by execute_webhook.
Trap all documented exceptions from maybe_execute_scaling_policy.
Add UnrecognizedCapabilityError to the logging test and,
use webhook_info_by_hash to test that the rest API does not wait for
webhook location to happen.
Merge pull request #280 from rackerlabs/auto-364-trap-webhook-exceptions

Trap more non-fatal exceptions when executing webhooks. (ready for review)