Refactor the way subdomain accounts are saved
    
    The original sysdb code had a strong assumption that only users from one
    domain are saved in the databse, with the subdomain feature, we have
    changed reality, but have not adjusted all the code arund the sysdb calls
    to not rely on the original assumption.
    
    One of the side effects of this incongrunece is that currently group
    memberships do not return fully qualified names for subdomain users as they
    should.
    
    In oreder to fix this and other potential issues surrounding the violation
    of the original assumption, we need to fully qualify subdomain user names.
    By savin them fully qualified we do not risk aliasing local users and have
    group memberhips or other name based matching code mistake a domain user
    with subdomain usr or vice versa.