UndertowSubsystemParser_5_0 could be instantiated twice: once as a reader and once as a writer

The org.wildfly.extension.undertow.UndertowSubsystemParser_5_0#xmlDescription could be created twice, the first and last line in the diff should return the same instance or use different approach: https://github.com/rhusar/wildfly/blob/7dbc8bd0c8bcdae5db61ecdff1484a422cf4b92c/undertow/src/main/java/org/wildfly/extension/undertow/UndertowExtension.java#L100-L113
Most likely the same issue is in multiple places.