org-capture: Fix bug when capturing with templates using `function'

org-capture: Fix bug when capturing with templates using `function'

* org-capture.el (org-capture): Store :return-to-wconf
earlier.
(org-capture-place-template): Don't store :return-to-wconf
when called from a capture template using `function', rely on
the early :return-to-wconf value store from `org-capture'.

Thanks to Brett Viren for raising this issue.