Update pom.xml

Per Adrian Nistor's comment on https://issues.jboss.org/browse/ISPN-2871

Also see: https://repository.jboss.org/nexus/service/local/repositories/releases/content/org/infinispan/infinispan-core/5.2.1.Final/
Merge pull request #1 from eddies/patch-1

Update pom.xml