fix #3036: add bg color to inputs

less/forms.less

@@ -71,6 +71,7 @@ select,
   font-size: @baseFontSize;
   line-height: @baseLineHeight;
   color: @gray;
+  background-color: @inputBackground;
   border: 1px solid @inputBorder;
   .border-radius(@inputBorderRadius);
 }