This commit fixes the integration tests and qa test after the reorganization to be
packaged as a single plugin.
Original commit: elastic/x-pack-elasticsearch@d6f488627f
- added the license-plugin dir as a src dir
- Made XPackPlugin customizable for tests. Now tests that need to plug in different behaviours (e.g. a custom license plugin) can do that by simply resetting the relevant delegee plugins (i.e. shield, marvel, license, watcher) in the ctor of a new XPackPlugin.
Original commit: elastic/x-pack-elasticsearch@ab83104955