sssd_id.py: Primary group should be returned for initgroups
Side effect of this change was that some primary groups
could not be resolved and therefore get_user_groups
failed in override tests. We should do the same as "id user".
return decimal representation GID if it cannot be mapped to name.
Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
(cherry picked from commit de19c0af27f1576c13bef183600136851baf767d)