Don't render disabled input elements white

public/css/icinga/forms.less

@@ -96,11 +96,6 @@ select::-moz-focus-inner {
   outline: 0;
 }
 
-input:disabled, select:disabled {
-    background-color: #fff;
-    border-color: white;
-}
-
 form.inline {
   margin: 0;
   padding: 0;
@@ -263,4 +258,4 @@ form > div.header {
   h1, h2, h3, h4, h5, h6 {
     display: inline-block;
   }
-}
+}