Read-Only mode doesn't actually work as expected

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It looks like setting read_only=True in Kazoo doesn't guarantee that Read-Only mode actually works (you have to turn it on in Zookeeper itself).

We need to clean up nd_service_registry so that it detects this behavior and lets the client know whether read_only mode is actually active or not. Right now the Lock code actually works even if you set read_only=True, which is very confusing.

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http://kazoo.readthedocs.org/en/latest/basic_usage.html?highlight=read%20only#read-only-connections