pam: sub-domain authentication fix
With a recent patch sysdb_getpwnam() was replaced by
sysdb_get_user_by_name() in the PAM responder. Unfortunately both behave
differently with respect to sub-domain users. As a consequence the PAM
responder was not able to resolve users from sub-domains. This patch
reverts this change and uses sysdb_getpwnam() again.
Reviewed-by: Alexander Bokovoy <abokovoy@redhat.com>