Change labs/cli/karaf to have their own parent POMs separate from the top-level POM

Currently, jclouds and jclouds-chef each have a parent POM, (repo)/project/pom.xml, which all the other POMs, including the top-level POM, in the project inherit from. jclouds-labs*, jclouds-cli and jclouds-karaf all just have the top-level POM, and everything else inherits from that top-level POM. That makes some processes (like aggregate javadoc and assemblies) done in the top-level POM a bit problematic for the first build of a new version (i.e., in releases). It'd be nice if these projects separated out the parent and top-level POM functionality as well.