CONFIG: Add subdomain_homedir to config locations
Option subdomain_homedir was missing from Python config API an
cfg_rules leading to config file validation failures. Add this option
into the necessary locations similar to other provider-generic domain
options.
Resolves:
https://pagure.io/SSSD/sssd/issue/3389
Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>
Reviewed-by: Fabiano Fidêncio <fidencio@redhat.com>
(cherry picked from commit beab60d88fc07d463f6fb3756c8f3d29bdd78827)