I found 2 bugs in MatchConvertorImpl.OfMatchToSALMatchConvertor().

1. MatchConvertorImpl.OfMatchToSALMatchConvertor() converts a switch port number
in IN_PORT match field into NodeConnectorId which contains only a logical port
name. But it should be converted into NodeConnectorId which contains a URI
of the specified port.

For example, if 3 is configured in IN_PORT match field and DPID is 1,
a string to be passed to constructor of NodeConnectorId is "openflow:1:3",
not "3".

2. Although CFI bit in VLAN_VID match field needs to be copied into MD-SAL match,
MatchConvertorImpl.OfMatchToSALMatchConvertor() does not.

Because of these bugs, openflowplugin generates incorrect OF13 flow statistics.
I wrote a patch and verified that it fixed this issue.