Fix Karaf integration tests

Now that Karaf compiles again (see JCLOUDS-41 and JCLOUDS-18) it would be nice if the integration tests worked again too. They are currently failing [1] because, as iocanel explains:

[14:29:34] Ioannis Canellos: the integration tests assume that the build artifacts are installed to the local maven repository
[14:29:44] Ioannis Canellos: if they are not found there the itests will fail
...
[14:30:39] Ioannis Canellos: so we have 2 options here: a) make sure we build using the install goal or refactor the itests so that they look under features module target dir

[1] https://jclouds.ci.cloudbees.com/view/integrations/job/jclouds-karaf/lastBuild/testReport/
[2] https://jclouds.ci.cloudbees.com/view/integrations/job/jclouds-karaf-1.6.x-branch/lastBuild/testReport/