WFLY-3189 - Do not use schema location in schema element. Do not use
schemaLocation when importing a namespace.

XML validators seem to get confused when schema location is specified
and imports / includes are circular. Instead rely on entries in XML
catalogue.

WFLY-3189 - retaining version attribute
Merge pull request #6739 from robstryker/WFLY-3189a

WFLY-3189 - Do not use schema location in schema element.