[SSSD] [PATCH] sss_override: support import and export

[Pavel Březina]

https://fedorahosted.org/sssd/ticket/2737

Hi, it should work... :-) However, I wanted to make import as 
transaction so no changes are made if some error occurs, but I had some 
troubles with it so I gave up eventually.

Of course, it would be quite difficult to make it safe across domains 
thus my intention was only to ensure that either all changes are done in 
a domain or none. But still leaving the possibility that changes are 
commited in one domain but cancelled in another.

I tried to start sysdb transaction on all used domains and then 
commit/cancel it, writing some neat mechanism for it. However, I 
occasionally run into a problem when data provider hangs when trying to 
safe a user. It looked like some sort of race condition.

Unfortunately I managed to delete the code so I can't show it to you, I 
think it would be a nice feature so if anyone familiar with ldb want to 
step in, he's welcome.