Also allows us to remove sysdb_subdom_get<pw/gr>nam() wrappers and restore
fqnames proper value in subdomains, by testing for a parent domain being
present or not.

Use the new authtok abstraction and interfaces throught the code.

Make it clear to the API users that we can not take arbitrary auth tokens.
We can only take a password for now so simplify and clarify the interface.

The monitor sends calls different sbus methods to different responders.
Instead of including headers of the particular responders directly in
monitor, which breaks layering a little, create a common header file
that will be included from src/responder/common/

The pam responder was not properly configured to recover from a backend
disconnect. The connections that were in flight before the disconnection
were never freed and new requests for the same user would just pile up on
top of the now phantom requests.

Fixes: https://fedorahosted.org/sssd/ticket/1655

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.