Fix: filter was not updated in file status queries

Due to the way the `q` variable was bound in the previous
implementation of the `setInterval` call, we were always querying the
file status using the filter (or lack thereof) that was in place in the
first show of the modal.

We now get the current value of `q` at the time in which the refresh
function is called.

See #2350

assets/js/components/respondents/RespondentIndex.jsx

@@ -137,14 +137,20 @@ class RespondentIndex extends Component<Props, State> {
     }
   }
 
-  showDownloadsModal() {
+  fetchFilesStatus() {
     const { projectId, surveyId, filter } = this.props
 
     // FIXME: don't fetch if we're already fetching
     this.props.surveyActions.fetchRespondentsFilesStatus(projectId, surveyId, filter)
+  }
+
+  showDownloadsModal() {
+    const { projectId, surveyId, filter } = this.props
+
+    this.fetchFilesStatus()
     if (this.state.filesFetchTimer == null) {
       const filesFetchTimer = setInterval(() => {
-        this.props.surveyActions.fetchRespondentsFilesStatus(projectId, surveyId, filter)
+        this.fetchFilesStatus()
       }, 20_000);
       this.setState({ filesFetchTimer })
     }