Comment 0 for bug 1410850

In multi domain setup keystone support only one SQL backend. Method that check how many SQL backends are requested contain error. It's result depends from domain's config load order. It will not detect multiple SQL backends if domain's config loaded in order like this: SQL -> not SQL -> SQL

And there is more potential issues with this limit on number of SQL backends.
First - if someone will call .setup_domain_drivers(...) multiple times(perhaps we should add self.crear() in this method or raise exception on second call of this method).
Second - .reload_domain_driver don't take in a count ._any_sql attribute. So if domain config will change backend type and it become SQL or become not SQL... we will have a problems.