[SUSE] Fix group ownership for SUSE (openSUSE & SLE)

SUSE systems (openSUSE and SUSE Linux Enterprise) do not create a group
for each user. It uses a general 'users' group.

Without this patch, SUSE users will get an error message like the
following when running `./dev setup-unit-tests`:

````
chown: invalid user: 'jamestyj.jamestyj'
````