Issues regarding uploading files to chat in the gui

Two issues I've noticed regarding uploading files to chat:
1. The downloaded file has the original uploaded filename, not the renamed name that the dialogue prompts for.
2. The keybase gui client is locked until that file manager process is closed.

This is with the desktop client on linux.

Also, for some reason the file manager keybase calls is `feh` for me (which only opens my `~/Downloads/` directory, not the file that should be opened, even when it's an image file), when `pcmanfm` should be my system default.

Start by reproducing both upload behaviors in the Linux desktop client: compare the renamed chat download with the original filename, then check why the GUI remains locked while the file manager is open. Also verify why feh is selected instead of the system default pcmanfm and whether an image opens as intended; done means all three behaviors work correctly.

Written by the indexing model from the issue text.