In essense these classes are Closeable but neither SolrSuggester nor Suggester close them at the core shutdown time.
I'm also not sure what the difference is between SolrSuggester and Suggester and whether both or them are needed. They seem awfully similar...
I've fixed the problem with the attached patch on
LUCENE-5650, but I'd appreciate if somebody with a deeper knowledge of Solr could chime in and confirm the patch is all right.