Dangling page lock on failing BTree traversals search ops due to excessive restarts

When a BTree search op is underway, it may have to restart due to concurrent structure modifications. If after 10 restarts another concurrent structure modification condition occurs, the search will exit, which can leave a dangling read lock, which will interfere with future modifications of the index page. In addition, wrong results will be returned, as the search simply returns early, with potentially wrong results.