COMPASS-212: Add min-height and overflow:scroll to dropdown in validation page (#572)

Author: Sean-Oh

src/internal-packages/validation/styles/option-selector.less

@@ -3,9 +3,13 @@
   padding: 0 5px;
 }
 
-
 .has-error .option-selector {
   button.dropdown-toggle {
     border-color: #843534;
   }
 }
+
+.open > .dropdown-menu {
+	overflow: scroll;
+    max-height: 200px;
+}