PROXY: Adding proxy_max_children option
The new option 'proxy_max_children' is applicable
in domain section. Default value is 10.
Resolves:
https://fedorahosted.org/sssd/ticket/3153
Reviewed-by: Fabiano Fidêncio <fidencio@redhat.com>
Reviewed-by: Pavel Březina <pbrezina@redhat.com>