Publish: fix Resume button not appearing after 'conflict' (#543)

## Issue
Apparently, a user is experiencing 423 locked errors from the server, which should not happen given the locking mechanism plus the user wasn't trying to do concurrent uploads.

## Fix
Anyway, fix the Resume button so that at least they can try to resume.

ui/redux/reducers/publish.js

@@ -184,7 +184,7 @@ export const publishReducer = handleActions(
         }
       } else if (status) {
         currentUploads[key].status = status;
-        if (status === 'error') {
+        if (status === 'error' || status === 'conflict') {
           delete currentUploads[key].uploader;
         }
       }