Test WildFly s390

We now have resources to test s390x with nightly jobs, and jobs running to do so:

Master / Linux s390x: https://ci.wildfly.org/viewType.html?buildTypeId=WF_MasterLinuxS390OpenJ911
Core / Linux s390x: https://ci.wildfly.org/viewType.html?buildTypeId=WildFlyCore_MasterLinuxS390OpenJ911

The release notes should perhaps say something like:

"Add s390x nightly CI tests using OpenJ9. This adds the s390x platform as part of the standard nightly validation tests. "