[FIX] web_editor: Avoid twice translated for static xml

Avoid texts to be translated twice if some modules have the translated
value corresponding to the English source term.

To reproduce: create a translation for static xml (comment 'openerp-web')
with 'Modifier' translated by 'Tadaaa'. In french context, the 'Edit'
button in forms is translated by 'Tadaaa'.

Don't translate template in web_editor if we are in the backend because
the translations of all the modules have already been loaded and applied.

addons/web_editor/static/src/js/base.js

@@ -32,7 +32,10 @@ data.dom_ready = dom_ready;
 var all_ready;
 data.ready = function () {
     if (!all_ready) {
-        all_ready = $.when(dom_ready, ajax.loadXML()).then(translations);
+        all_ready = $.when(dom_ready, ajax.loadXML());
+        if (!odoo._modules) {
+            all_ready.then(translations);
+        }
     } else if(all_ready.state() === "resolved") { // can add async template
         all_ready = $.when(dom_ready, ajax.loadXML());
     }