SOLR-6224: Post soft-commit callbacks are called before soft commit actually happens

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_5x@1633677 13f79535-47bb-0310-9956-ffa450edef68
SOLR-6295: Fix child filter query creation to never match parent docs in SolrExampleTests

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_5x@1633680 13f79535-47bb-0310-9956-ffa450edef68