[FIX] web: form: remove o_field_invalid class when not necessary

Before this commit, the o_field_invalid class was not removed once an
invalid field becomes valid, until the user saves the form view (which
will rerender the full view anyway)

addons/web/static/src/js/views/form/form_renderer.js

@@ -84,6 +84,9 @@ var FormRenderer = BasicRenderer.extend({
             _.each(resetWidgets, function (widget) {
                 self._setIDForLabel(widget, self.idsForLabels[widget.name]);
             });
+            if (self.$('.o_field_invalid').length) {
+                self.canBeSaved(self.state.id);
+            }
             return resetWidgets;
         });
     },

addons/web/static/tests/views/form_tests.js

@@ -2273,7 +2273,6 @@ QUnit.module('Views', {
             "input should be tagged as invalid");
 
         form.$('input').val("tralala").trigger('input');
-        form.$buttons.find('.o_form_button_save').click();
 
         assert.strictEqual(form.$('.o_field_invalid').length, 0,
             "nothing should be marked as invalid");