Zookeeper is unable to set the zookeeper.sasl.client.canonicalize.hostname using system variable

After some reworking on the Zookeeper Sasl implementation (https://issues.apache.org/jira/browse/ZOOKEEPER-3156) the knob of zookeeper.sasl.client.canonicalize.hostname was introduced in order to disable the host name canonicalization. However in ZKClientConfig in handleBackwardCompatibility() this option is not included, which I assume is due to omission. This creates an issue if the zookeeper library is hidden behind another library that does provide an interface to change this value.

Therefore it should also be set by the system properties like the rest of the variables.