AD_PROVIDER: Initializing of ad_enabled_domains
We add ad_enabled_domains into ad_subdomains_ctx.
Resolves:
https://fedorahosted.org/sssd/ticket/2828
Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>
(cherry picked from commit a82baf596bac1fdac6addca6419d8992111a8aa2)