Celery: RunTimeError: Acquire on closed pool try to use control inspect

Checklist

• [x] I have included the output of celery -A proj report in the issue.
  (if you are not able to do this, then at least specify the Celery
  version affected).

software -> celery:4.0.2 (latentcall) kombu:4.1.0 py:2.7.13 or (py:2.7.12)
billiard:3.5.0.3 redis:2.10.5
platform -> system:Darwin arch:64bit imp:CPython . (though usually: system:Linux arch:64bit, ELF)
loader -> celery.loaders.app.AppLoader
settings -> transport:redis results:redis://localhost:6380/

BROKER_TRANSPORT_OPTIONS: {
'fanout_patterns': True, 'fanout_prefix': True}
CELERY_TASK_COMPRESSION: 'gzip'
CELERY_TIMEZONE: 'UTC'
CELERY_RESULT_SERIALIZER: 'json'
CELERY_BROKER_URL: u'redis://localhost:6380//'
CELERY_TASK_SERIALIZER: 'json'
CELERY_RESULT_EXPIRES: 60
CELERY_ACCEPT_CONTENT: ['application/json']
TIME_ZONE: 'UTC'
CELERY_MESSAGE_COMPRESSION: 'gzip'
CELERY_TASK_ALWAYS_EAGER: False
CELERY_RESULT_BACKEND: u'redis://localhost:6380/'

• [x] I have verified that the issue exists against the master branch of Celery.

Also occurs on celery 4.1.0.

Steps to reproduce

Try to use the control module. In my case, I'm getting the active_queues().

Expected behavior

I expect that so long as the system is in a good state, I should be able to get the info from within the control module. I don't understand exactly why sometimes the pool is closed and other times it's not.

Actual behavior

This might be the same issue as in #1839

The code will have a runtime error, so I am unable to query for the data I need from celery.

File "/.../tasks.py", line 80, in workers_on_queue
    for k, v in six.viewitems(celery_app.control.inspect().active_queues()):
  File "/.../lib/python2.7/site-packages/celery/app/control.py", line 116, in active_queues
    return self._request('active_queues')
  File "/.../lib/python2.7/site-packages/celery/app/control.py", line 81, in _request
    timeout=self.timeout, reply=True,
  File "/.../lib/python2.7/site-packages/celery/app/control.py", line 436, in broadcast
    limit, callback, channel=channel,
  File "/.../lib/python2.7/site-packages/kombu/pidbox.py", line 315, in _broadcast
    serializer=serializer)
  File "/.../lib/python2.7/site-packages/kombu/pidbox.py", line 285, in _publish
    with self.producer_or_acquire(producer, chan) as producer:
  File "/usr/local/Cellar/python/2.7.13_1/Frameworks/Python.framework/Versions/2.7/lib/python2.7/contextlib.py", line 17, in __enter__
    return self.gen.next()
  File "/.../lib/python2.7/site-packages/kombu/pidbox.py", line 247, in producer_or_acquire
    with self.producer_pool.acquire() as producer:
  File "/.../lib/python2.7/site-packages/kombu/resource.py", line 74, in acquire
    raise RuntimeError('Acquire on closed pool')

This only happens when we're using the control module. Sometimes it works okay.

This code path was even in a retry-loop, so in the end it still failed to execute.