ERROR dial unix /run/user/1012/keybase/keybased.sock: connect: permission denied

I installed keybase on ubuntu 16 as a non root user with sudo priveleges. Afterwards I ran `run_keybase`. I assumed this would install for all users.

However when I try to user keybase with another user I'm getting this error:
```
ERROR dial unix /run/user/1012/keybase/keybased.sock: connect: permission denied
```

The socket seems to be owned by the user who installed keybase. However seem grant execute to all users?
```
srwxrwxr-x 1 james james 0 Oct 17 20:38 keybased.sock
```

Start by reproducing the failure with run_keybase on Ubuntu 16 and inspect access to /run/user/1012/keybase/keybased.sock as both users. Trace how the per-user socket is created and determine the expected multi-user behavior; done means another user can use Keybase without a permission-denied error.

Written by the indexing model from the issue text.