ptserver: fix pt_util creation of groups
In commit
53ac98931adf9f04c150d9bc084cae31f3913476 the adjustment of
owner id was moved from CreateEntry() into CreateGroupName(). This was
done for two reasons:
1. to reuse the computation of "is administrator" within
CreateGroupName() in order to permit the owner id to be set
to the invalid values 0 and ANONYMOUSID.
2. to allow the owner id to be altered in ChangeEntry().
Unfortunately, CreateEntry() needs to be able to alter the owner id
when creating users not only groups.
This change moves the computation of "is administrator" and the
owner id assignment to CreateEntry() and ChangeEntry().
Change-Id: I0d37f5a43ea5919d1bbc3ba6d82b2924ab38befc