Remove template_retry config section. Add new vault.retry section which only has num_retries field; if num_retries is 0 or absent, default it to 12 for backwards compat with pre-1.7 template retrying. Setting num_retries=-1 disables retries.
Configured retries are used for both templating and api proxy, though if template requests go through proxy (currently requires persistence enabled) we'll only configure retries for the latter to avoid duplicate retrying. Though there is some duplicate retrying already because whenever the template server does a retry when not going through the proxy, the Vault client it uses allows for 2 behind-the-scenes retries for some 400/500 http error codes.
