PacketType.getLength() says its 4 bytes, but its really 6

[rsharo]

org.projectfloodlight.openflow.types.PacketType returns 4 from getLength(). It also implements write4Bytes() and read4Bytes() methods, but these methods actually read/write 6 bytes.

[rsharo]

Found while working on unit tests for Writeable implementations for OFValueType (PR #505). Leaving this bug alone for now since I don't know who would be impacted downstream if I changed it.