Automatic merge from submit-queue

Delete the broken Celery+RabbitMQ example

The celery container used in the example is broken and does not come up
on most distros. The e2e test that was validating this example was not
detecting the fact the celery pod was crash looping. 
I attempted to fix the celery container, but it proved to be tedious.
The proposed fix is to update the glibc version to >= 2.23. In this case
it requires updating the python docker image and the celery base image.

https://github.com/kubernetes/kubernetes/issues/31456
has more details. 

I'm deleting the example instead of marking it as broken because a user
might overlook the broken warning and it should be trivial to revert
this PR if someone can fix the celery container.