fix(virtual-background): Hide scrollbar on loading action.

css/modals/virtual-background/_virtual-background.scss

         margin-right: 5px;
     }
 }
+
+.modal-dialog-form .virtual-background-loading {
+    overflow: hidden;
+}
 .file-upload-btn {
     display: none;
 }

react/features/virtual-background/components/VirtualBackgroundDialog.js

             titleKey = { 'virtualBackground.title' }
             width = 'small'>
             {loading ? (
-                <div>
+                <div className = 'virtual-background-loading'>
                     <span className = 'loading-content-text'>{t('virtualBackground.pleaseWait')}</span>
                     <Spinner
                         isCompleting = { false }