SOLR-6087: 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 ticket. The baseline of the diff is the https://issues.apache.org/jira/i#browse/SOLR-6067 refactor i.e. https://github.com/apache/lucene-solr/pull/48 diff/branch.

An alternative/open question is if a 'finally call finish' for the try-catch might be okay, though 'finish' itself might throw and any exception thrown by the finish would mask any non-TimeLimitingCollector non-EarlyTerminatingCollectorException exception thrown by IndexSearcher.