I found an infinity loops bug. We have to fix that for Solr plugin 3.x and 4.x, too. Karl, Will you fix this?

git-svn-id: https://svn.apache.org/repos/asf/manifoldcf/trunk@1547669 13f79535-47bb-0310-9956-ffa450edef68
Merge in connector-pool refactoring from CONNECTORS-781 branch.

git-svn-id: https://svn.apache.org/repos/asf/manifoldcf/trunk@1548081 13f79535-47bb-0310-9956-ffa450edef68
Create a rebased branch to continue work on CONNECTORS-781

git-svn-id: https://svn.apache.org/repos/asf/manifoldcf/branches/CONNECTORS-781@1548084 13f79535-47bb-0310-9956-ffa450edef68