Update Docker socket ownership
Summary:
In D2668, the group name allowed to connect to Docker socket is customized.
Yet, on Dwellers, the docker client still can't connect on it.
There is a similar known issue reported upstream, which suggests the socket
systemd unit used for socket-activated services also needs to be aware
of the group.
References:
Ref T1724
Test Plan: docker ps on Dwellers
Reviewers: dereckson
Reviewed By: dereckson
Tags: #user-dorianwinty
Maniphest Tasks: T1724
Differential Revision: https://devcentral.nasqueron.org/D2670