[WFLY-1938] mod_cluster subsystem needs transformation to 1.3.0 and 1… 

https://issues.jboss.org/browse/WFLY-1938
https://issues.jboss.org/browse/WFLY-2240
https://issues.jboss.org/browse/WFLY-2303
https://issues.jboss.org/browse/WFLY-2304

In short:

* adds missing transformations
* adds corresponding tests
* fixes XSD schema
* fixes validation of session draining strategy