Fix focus styles in admin form controls

We lost focus styles on certain controls in commit 4dad04ae3, since we
were applying a border with a rule which had more precedence than the
rule of border on focus.

app/assets/stylesheets/admin.scss

@@ -274,6 +274,10 @@ $table-header:   #ecf1f6;
       border: $admin-border;
       border-radius: rem-calc(6);
       box-shadow: none;
+
+      &:focus {
+        border: $input-border-focus;
+      }
     }
   }
 

app/assets/stylesheets/layout/locale_switcher.scss

@@ -39,6 +39,7 @@
       width: auto;
 
       &:focus {
+        border: 0;
         outline: $outline-focus;
       }