privilege role selector: fix renderer for Proxmox VE

privilege role selector: fix renderer for Proxmox VE

In PBS we get an array here, so the renderer is fine, but in pve it's
just a long string, so add a space after commas to achieve the same
effect.

Without this, the second column is not visible in pve because of an
error in the renderer (no 'join' function on a string)

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
 [ T: squash in code-reduction to make it a one-liner again ]
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>