[SSSD] [PATCH] Use refcount to keep track of server structures returned from failover

[Jakub Hrozek]

Hi,

the attached patches are my proposal to fix
https://fedorahosted.org/sssd/ticket/2829

I haven't tested them past make check yet, because I'm not sure I like
them myself :) but at the same time I can't see a better way to keep
track of the servers and let callers set state of servers.

The most ugly thing so far IMO is the fo_internal_owner member. I would
prefer to instead have a fo_server_wrap structure that would be used for
the server_list, but I didn't want to do a large change before we agree
the refcount is a good idea at all.

The other ugly side-effect is that we need to be sure that nobody calls
talloc_free on the fo_server structure. Instead, only the parent context
can be freed (that's also what the first patch is about).