[FIX] website_sale: fix zoom wich was not always computed

In some case, (many JS like runbot with all modules), the onload event was
binded after that the image was loaded. So the JS code that make the zoom
conditionnal was not executed.

Now we apply the function on all images already loaded, or that will is loading

Courtesy of @ged-odoo for help and review

addons/website_sale/static/src/js/website_sale.js

@@ -482,16 +482,22 @@ odoo.define('website_sale.website_sale', function (require) {
         }
     });
 
+    function onImageLoaded(img, callback) {
+        $(img).on('load', function() { callback(); });
+        if (img.complete) {
+            $(img).off('load');
+            callback();
+        }
+    }
+
     // Do not activate image zoom for mobile devices, since it might prevent users from scrolling the page
     if (!config.device.isMobile) {
-
         var autoZoom = $('.ecom-zoomable').data('ecom-zoom-auto') || false,
         factorZoom = parseFloat($('.ecom-zoomable').data('ecom-zoom-factor')) || 1.5,
         attach = '#o-carousel-product';
         _.each($('.ecom-zoomable img[data-zoom]'), function (el) {
-            var $img = $(el);
-            $img.load(function(e) {
-                var el = e.currentTarget;
+            onImageLoaded(el, function() {
+                var $img = $(el);
                 if (!_.str.endsWith(el.src, el.dataset.zoomImage) || // if zoom-img != img
                     el.naturalWidth >= $(attach).width() * factorZoom || el.naturalHeight >= $(attach).height() * factorZoom) {
                     $img.zoomOdoo({event: autoZoom ? 'mouseenter' : 'click', attach: attach});
@@ -502,4 +508,5 @@ odoo.define('website_sale.website_sale', function (require) {
             });
         });
     }
+
 });