Test containers running simultaneously are not isolated

Due to RESTEASY-1884 new container was added to arquillian.xml that can run simultaneously with the default one. Running two or more instances from the same server home, ie. the same configuration, log and data directories isn't correct approach.

The better approach seems to be use isolated copies of standalone dirs together with usage of -Djboss.server.base.dir property. This way the server home can be shared while instance specific stuff is isolated.