PLT-2755 Shortcut to upload file (#2967)

* wrong ref

* Changed back to CTRL+U

* Fixed scope of fileUpload

* Removed stray comma

webapp/components/file_upload.jsx

@@ -284,7 +284,10 @@ class FileUpload extends React.Component {
 
     keyUpload(e) {
         if ((e.ctrlKey || e.metaKey) && e.keyCode === Constants.KeyCodes.U) {
-            $(this.refs.input).focus().trigger('click');
+            e.preventDefault();
+            if (this.props.postType === 'post' && document.activeElement.id === 'post_textbox' || this.props.postType === 'comment' && document.activeElement.id === 'reply_textbox') {
+                $(this.refs.fileInput).focus().trigger('click');
+            }
         }
     }