FELIX-4279, FELIX-4280:

- ensure the org.osgi.service.useradmin package is exported by our
  implementation as well;
- ensure the correct import dependencies are used, without hard
  dependencies on other optional services (such as EventAdmin);
- stripped the itests from all redundant bundles to verify this.



git-svn-id: https://svn.apache.org/repos/asf/felix/trunk@1531234 13f79535-47bb-0310-9956-ffa450edef68