POSIX and Windows meterpreter, inconsistent return types for interface in routes

[todb-r7]

This issue was RM8702, originally filed by by @jlee-r7

Expected:
The interface attribute of Rex::Post::Meterpreter::Extensions::Stdapi::Net::Route should be comparable to an attribute on Rex::Post::Meterpreter::Extensions::Stdapi::Net::Interface. As it stands, Windows returns a Stringified version of Interface#index, while Linux returns Interface#mac_name.

Actual:
In this example, I have two sessions, the first Windows, the second Linux.

framework.sessions.values.each { |s| p s.net.config.routes.first.interface }; nil
# Returns:
"11"
"eth0"

---

@OJ asked what it should look like, and @jlee-r7 responded: I think that depends on whether we can rely on Linux's indexes to remain consistent. If so, then it should just be a TLV_TYPE_UINT for the index on both. Otherwise, I think we have to use the name, which sorta sucks because they're ridiculous on windows.

@jlee-r7 also provided a workaround on the Ruby side, here:
jlee-r7/metasploit-framework@c6e1e59#diff-6f1044d7b2cf3f1f66d9c1871ede170cR327