PHP-1065: Fix double free() when OP_GET_MORE fails

This is a bad copy&paste from the normal MongoCursor ctor
PHP-1065: Don't try to kill cursor that don't have a connection
Add a testcase for PHP-1065
Merge pull request #672 from bjori/PHP-1065-segfault-after-get-more-failure

Php 1065 segfault after get more failure

* bjori/PHP-1065-segfault-after-get-more-failure:
  Add a testcase for PHP-1065
  PHP-1065: Don't try to kill cursor that don't have a connection
  PHP-1065: Fix double free() when OP_GET_MORE fails