Improper default for RabbitMQ Management API URL

[skodde]

Hi,

It seems that from PR #896 (released with 0.9.4) broker_api (http_api) defaults to the same port of the broker (broker_url) inherited from Celery, in addition to the same user, address, etc., instead of continuing to hardcode the port as 15672.

flower/flower/utils/broker.py

Lines 52 to 56 in 30b5a97

	if not http_api:
	http_api = "http://{username}:{password}@{host}:{port}/api/{vhost}".format(
	username=self.username, password=self.password,
	host=self.host, port=self.port, vhost=self.vhost
	)

vs.

flower/flower/utils/broker.py

Lines 58 to 60 in 95e9f84

	if not http_api:
	http_api = "http://{0}:{1}@{2}:15672/api/{3}".format(
	self.username, self.password, self.host, self.vhost)

This seems counterproductive and appears to have broken several configurations in the wild.

RabbitMQ does not appear to support having the Management plugin listening on the same port as the AMQP listener, so there should not be a use case for this default.

On the other hand, using the same port as the default Management plugin listener (15672) would allow it to work without any additional Flower specific configuration, as it did in the past.