rshd: close pam session correctly
    
    When client does not ask for separate error channel rshd will execute
    the requested command on top of itself, thus is never able to close
    opened pam session. In addition it then closes all file descriptors
    except stdin, stdout and stderr. This closing of descriptors will
    close descriptor used by pam_systemd module and triggers logind to
    kill the process.
    
    Patch contributed by Tom Hughes, <tom@compton.nu>
    
    Resolves RHBZ #896583.
    
    Signed-off-by: Michal Sekletar <msekleta@redhat.com>