Add bottom margin for flash container on login page

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/assets/stylesheets/pages/login.scss

@@ -8,6 +8,10 @@
     max-width: none;
   }
 
+  .flash-container {
+    margin-bottom: $gl-padding;
+  }
+
   .brand-holder {
     font-size: 18px;
     line-height: 1.5;