LUCENE-5067: add more tests

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1587627 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5604: switch these 'many terms' tests back to previous adversarial hash conflict case

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1587684 13f79535-47bb-0310-9956-ffa450edef68
switch case fallthrough is OK here

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1587691 13f79535-47bb-0310-9956-ffa450edef68
 SOLR-5904: ElectionContext can cancel an election when it should not if there was an exception while trying to register as the leader. 

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1587703 13f79535-47bb-0310-9956-ffa450edef68
SOLR-5954: Slower DataImportHandler process caused by not reusing jdbc connections.

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1587707 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5606: un-ignore monster tests, instead annotate with a test group so they can be optionally run

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/branch_4x@1587771 13f79535-47bb-0310-9956-ffa450edef68
pulling in changes from solr2052 on trunk