LDAP/AD: Do not fail in case rfc2307bis_nested_groups_recv() returns ENOENT
    
    Commit 25699846 introduced a regression seen when an initgroup lookup is
    done and there's no nested groups involved.
    
    In this scenario the whole lookup fails due to an ENOENT returned by
    rfc2307bis_nested_groups_recv(), which leads to the user removal from
    sysdb causing some authentication issues.
    
    Resolves:
    https://pagure.io/SSSD/sssd/issue/3331
    
    Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
    Reviewed-by: Sumit Bose <sbose@redhat.com>
    (cherry picked from commit df4b24bed15f45bf286fb0102fd397218fdd4186)
    (cherry picked from commit 4540d9f6817c78eef7b6e2d79245434811b59ad9)