Remove WildFly BoM import from Hawkular Parent POM

WildFly BoM import [1] needs to be removed from Hawkular Parent POM. It was required by Hawkular Metrics team. They i.a. say that some of their modules need to support containers (or container versions) other than the WildFly imported in the Parent POM.

[1] https://github.com/hawkular/hawkular-parent-pom/blob/8171c18a6fe050e902c52ae3557612ccd52fbafe/pom.xml#L276-L282