Add waitForCompletion option to config endpoint

Currently, the config endpoint will return immediately after persisting configuration and kicking off the OSGi component life cycle. Routes affected by the configuration change may be in a state of flux (either operating with old config, not available, or operating with new config) without a way for a caller to determine know when it's okay to proceed. Adding an option similar to the sync endpoint to waitForCompletion will allow callers, functional tests, the admin UI, or IC, to ensure config changes have been consumed.

Acceptance Criteria

• Calling the config endpoint with waitForCompletion=true should guarantee the configuration has been consumed by respective components. For example, changing a connector's config should cause the endpoint to wait until the connector and its endpoint are ready to be used.
• The config endpoint should still return at some point if config with a bad field is submitted even with the waitForCompletion=true flag
• The config endpoint should still return at some point if the config does not correspond to an existing component.