This patch introduces a new way for configuring which handlers the
Kuryr controller should be using. This will allow people to use
externally provided handlers as long as they are installed as
entrypoints of the right namespace.
Implements: blueprint kuryr-pluggable-handlers
Change-Id: I52ce0ef00771c8587d7f7113cc5eb4839d1309a5
Signed-off-by: Antoni Segura Puimedon <antonisp@celebdor.com>