Fix/port access

[xinyuli1204]

auto p = new Port(reinterpret_cast<Port>(obj));
p->set_index(index);
*ptr = reinterpret_cast<ion_port_t>(p);
reinterpret_castion::Port*(obj)->set_index(index);

obj doen't need to set_index, otherwise have issue on following example

p0 = ports[0]
p1 = ports[1]
when access ports again, the index of ports will be 0 instead of -1