Add user and group for dugong

This CL will allow us to give dugong permission to control the dbus
interface for making requests for TEE bringup.

BUG=b:162096925
TEST=none

Change-Id: I1fbe4dcbab40a2ef573b6d69e0409f8a57c55c25
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/eclass-overlay/+/2495485
Tested-by: Nicole Anderson-Au <nvaa@google.com>
Reviewed-by: Allen Webb <allenwebb@google.com>
Commit-Queue: Nicole Anderson-Au <nvaa@google.com>