Merge branch 'login-flash' into 'master'

Add bottom margin for flash container on login page
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

cc @jschatz1 @skyruler 

Fixes #13935 

See merge request !3040

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;