SolrIndexSearcher makes no DelegatingCollector.finish() call when ...

SolrIndexSearcher makes no DelegatingCollector.finish() call when IndexSearcher throws an expected exception. This seems like an omission.

This pull request is for https://issues.apache.org/jira/i#browse/SOLR-6087 re-baselined against trunk which now contains the SOLR-6067 refactor.