Added session-keyfile statement into default named.conf since we use /run/named
    
    Since we don't use default /var/run/named path for PID file, we should not
    use it also for Dynamic DNS session key.
    
    Therefore the following line was added into the named.conf:
    session-keyfile "/run/named/session.key";
    
    Signed-off-by: Tomas Hozza <thozza@redhat.com>