Title: #905: Don't ignore host entries in Group Policy security filters
@pbrezina Thanks for reviewing! I've fixed the issues you commented on, as well as one
of my own. I noticed that the sssd-ad man page still contained a comment explaining that
host entries in the Security Filter were not supported, so I removed that statement.
The last commit contains few `FIXMEs`. Can you address them as well?
Or what are the consequences if they are not addressed?
The FIXME in sysdb_set_computer would be an enhancement, but is not required for
this to function.
The FIXME in ad_gpo_get_host_sid_retrieval_done is trivial, and not necessary.
See the full comment at https://github.com/SSSD/sssd/pull/905#issuecomment-561767891