don't processEvents during rollback

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1586946 13f79535-47bb-0310-9956-ffa450edef68
tests: harden this test due to a current short coming in the collections api.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1587099 13f79535-47bb-0310-9956-ffa450edef68
SOLR-5980: Add a test.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1587149 13f79535-47bb-0310-9956-ffa450edef68