STANBOL-1081: fixed two other small issues with the unregistration of registered components. ServiceRegistrations where unregistered twice (via the API and the Solr CloseHook#preClose) if the close was originating from an API call the the SolrServerAdapter.

git-svn-id: https://svn.apache.org/repos/asf/stanbol/trunk@1490571 13f79535-47bb-0310-9956-ffa450edef68