Fix upload file into search page unnecessary POST (#2200)

## Which problem is this PR solving?
- Resolves #2192

## Description of the changes
- Remove uploading files into the search page unnecessary POST

## How was this change tested?
Manually tested.

## Checklist
- [x] I have read
https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
- [x] I have signed all commits
- [ ] I have added unit tests for the new functionality
- [x] I have run lint and test steps successfully
  - for `jaeger`: `make lint test`
  - for `jaeger-ui`: `yarn lint` and `yarn test`

Signed-off-by: tico88612 <[email protected]>

packages/jaeger-ui/src/components/SearchTracePage/FileLoader.tsx

@@ -28,9 +28,10 @@ export default function FileLoader(props: FileLoaderProps) {
   return (
     <Dragger
       accept=".json"
-      beforeUpload={(file, fileList) =>
-        fileList.forEach(fileFromList => props.loadJsonTraces({ file: fileFromList }))
-      }
+      beforeUpload={(file, fileList) => {
+        fileList.forEach(fileFromList => props.loadJsonTraces({ file: fileFromList }));
+        return false;
+      }}
       multiple
     >
       <IoDocumentAttachOutline className="Dragger--icon" />