Bump tested version to 4.1


git-svn-id: https://plugins.svn.wordpress.org/hyperdb/trunk@1046506 b8457f37-d9ea-0310-8a92-e5e31aec5664
Merge https://github.com/wp-plugins/hyperdb
$this->dbh is null on network errors

check_tcp_responsiveness will never allow $this->dbh to be set, so let's
check it before we do anything.