[BUG] Drag&Drop 2 or more files into chat uploads all, but only shows one.

Reproduce:

1. Open a chat while logged in as abc with the account def.
2. With the chat opened, select two files on your desktop, drag and drop them on the chat window.
3. Click "Send" for each file.
4. Only the last one is shown on abc's screen in the chat. (Restarting Keybase will show both files, but until then abc will only ever see the last file as being uploaded.)
5. On def's screen they will see both files in the chat window for download.
6. Funnily, After uploading, the last file is shown on abc's screen, but if you switch to another chat on abc's client, and then switch back, only the first file is shown.

This causes users to upload like 50 files, because they keep trying to drag and drop a bunch, multiple times, and getting confused.

No files or tests are named in the issue. Reproduce the drag-and-drop sequence in a chat, then compare the sender's view immediately after each upload with the recipient's view and after switching chats. Done means the sender sees every uploaded file without restarting or changing chats.

Written by the indexing model from the issue text.