support container znodes

[rgs1]

This is now merged on trunk and on the 3.5 branch of ZooKeeper: https://issues.apache.org/jira/browse/ZOOKEEPER-2163 (see apache/zookeeper@48f0269).

It might be backported for the upcoming 3.4.7 release too, so it would be nice to support it.

[teeeg]

Would this be something that maintainers would want to add to Kazoo? Is it feasible at this point in time? I would have an interest in doing the work to support containers if there's interest from the community.

[rgs1]

@teeeg i am happy to help with reviews.

[teeeg]

@rgs1 do you have an idea of the feasibility of supporting containers? how much work do you suppose it is?

[StephenSorriaux]

@teeeg Yes, that would be a nice feature.

[rgs1]

@teeeg should be pretty straight fwd, given that container requests are basically create requests with a different opcode:

https://github.com/envoyproxy/envoy/blob/master/source/extensions/filters/network/zookeeper_proxy/filter.cc#L134