[FIX] portal: verify input content instead of body

When running the portal tour, the test succeed too early because it finds
the words "Your Details" on the wrong page (/my instead of /my/account).
The selector has a match on previous page, so tour succeeded when it 's
not complete.

This commit use another selector that only match on the '/my/account'
page.

addons/portal/static/src/js/portal_tour.js

@@ -14,7 +14,7 @@ tour.register('portal_load_homepage', {
         },
         {
             content: "Load my account details",
-            trigger: 'body:contains("Your Details")',
+            trigger: 'input[value="Demo Portal User"]'
         }
     ]
 );