[spp] Cannnot add pcap PMD and null PMD via spp.py

[Hideyuki Yamashita <yamashita.hideyuki@po.ntt-tx.co.jp>]

Hello,

I am testing spp through spp-ctl/spp.py.

I encounter error when
- adding pcap PMD
- adding null PMD
though spp.py.

When I look source code of spp_webapi.py,
it looks type is not defined for neither null PMD or pcap PMD. 

    def _validate_port(self, port):
        try:
            if_type, if_num = port.split(":")
            if if_type not in ["phy", "vhost", "ring"]: //problematic    
                raise
            int(if_num)
        except:
            raise KeyInvalid('port', port)

It is highly appreciated that someone provide resolution on this.

Thanks in advance.

BR,
Hideyuki Yamashita
NTT TechnoCross