i've logged a defect with regard to this problem.  [NIM094284: Bing address locator always uses HTTP]in the meantime, you could use a technique similar to what is described in the forum thread Vinay linked to to manually update the url for the request in your code.esriRequest.setRequestPreCallback(myCallbackFunction);
...
function myCallbackFunction(ioArgs) {         
    if (ioArgs.url == "http://serverapi.arcgisonline.com/veadaptor/production/services/geocode/geocode") {
        ioArgs.url = "https://serverapi.arcgisonline.com/veadaptor/production/services/geocode/geocode";
    }
    // don't forget to return ioArgs.
    return ioArgs;
}sorry for the inconvenience!