trunks: Add trunks user and group

Add trunks user and group to eclass. This allows trunks daemon
to adopt its dbus interface with the trunks user

BUG=chromium:372012
TEST=ran this autotest
CQ-DEPEND=CL:214025

Change-Id: I31eade61c831c06625586292f694b33bfdb0aa6e
Reviewed-on: https://chromium-review.googlesource.com/214228
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Commit-Queue: Utkarsh Sanghi <usanghi@chromium.org>
Tested-by: Utkarsh Sanghi <usanghi@chromium.org>
2 files changed