[BUG] Multiple email queue after a successful File Export on multiple clicks.

Description:

On FIleExport, When a user clicks multiple times on Export, the email for sending the export messages
is queued multiple times.

Steps to reproduce:

1. Open any Channel, Go to 3 dots on the Top-Right Corner.
2. Click on Export messages.
3. On Method, choose Export as file and choose the date duration.
4. Try clicking multiple times on Export

Expected behavior:

Expected behaviour should be, Once the email is successfully queued for the export, the Contextual Bar must be closed.

Actual behavior:

After successful queue, you can click multiple times on Export.

Server Setup Information:

• Version of Rocket.Chat Server: 3.14.0-develop
• Operating System: Gitpod-linux
• Deployment Method:
• Number of Running Instances:
• DB Replicaset Oplog:
• NodeJS Version: 12.22.1 - x64
• MongoDB Version: 4.2.8

Client Setup Information

• Desktop App or Browser Version:
• Operating System:

Additional context

https://user-images.githubusercontent.com/53378650/115986049-1d64f880-a5cc-11eb-824e-07799d47ca82.mp4

Relevant logs:

Start by reproducing the FileExport flow described in the issue, then trace the Export action and contextual bar behavior. Done means a successful export queue closes the contextual bar and repeated clicks do not queue additional emails.