This sysdb_req has always really been a transaction handle and not
a request.

This is part of a set of patches to rewrite transaction support in sysdb to a
hopefully better API, that will also let use use tevent_req async style to
manipulate our cache.

Convert auth modules to do the caching themselves

Change sysdb to always passwd sss_domain_info, not just the domain name.
This way domain specific options can always be honored at the db level.

To be able to correctly filter out duplicate names when multiple non-fully
qualified domains are in use we need to be able to specify the domains order.

This is now accomplished by the configuration paramets 'domains' in the
config/domains entry. 'domains' is a comma separated list of domain names.
This paramter allows also to have disbaled domains in the configuration without
requiring to completely delete them.

The domains list is now kept in a linked list of sss_domain_info objects.
The first domain is also the "default" domain.

Now it can load from scratch default configuration that is valid for all
daemons.
First thing, make it possible for each daemon/provider to set its own debug
level in its configuration entry.

Per discussion with the desktop team, using the org.freedesktop
interface name will simplify adoption, as potential users won't
feel like they're pulling in a FreeIPA dependency.

Also add accidentally-omitted loginShell parameter.