The kubernetes python client has a bug [1] which results in frequent
deadlocks while being cleaned up, which causes armada to hang at the
end of execution.
This patchset works around that issue by mocking out the associated
thread pools, since they are only needed for async kubernetes api
calls, which armada does not use.
[1]: https://github.com/kubernetes-client/python/issues/411
Change-Id: I71fbfbe355347ae2ddd02ffd26d881368320246b
673b1ed4bc