Fix the java.lang.NoClassDefFoundError: org/xnio/OptionMap error

This commit should fix the following bug:
16:38:24,488 ERROR [io.undertow.request] (default task-14) UT005023: Exception handling request to /javax.faces.resource/select2.css.html: java.lang.NoClassDefFoundError: org/xnio/OptionMap
	at org.keycloak.adapters.undertow.SavedRequest.trySaveRequest(SavedRequest.java:49) [keycloak-undertow-adapter-1.1.0.Beta-18122014.jar:1.1.0.Beta-18122014]