[dns-client] use 'Header::SetRandomMessageId()' to set query message ID (#6061)
[dns-client] use 'Header::SetRandomMessageId()' to set query message ID (#6061)


openthread/openthread,jwhui/openthread,abtink/openthread,srickardti/openthread,srickardti/openthread,jwhui/openthread,abtink/openthread,openthread/openthread,jwhui/openthread,abtink/openthread,openthread/openthread,jwhui/openthread,srickardti/openthread,openthread/openthread,srickardti/openthread,abtink/openthread