Undertow listener max-post-size attribute default value discrepancy

There is a discrepancy in undertow schema definition of listener attribute 'max-post-size' default value here and ListenerResourceDefinition here.

These two default values should be unified so they match.

NOTE: I set GA as a target release as this is probably trivial change in Undertow schema definition which is better to do before GA as after that any change into schema is difficult.