fix: socklen_t initialization

[samuelemusiani]

I've noticed that sometimes, when you try to connect to a wirefilter cable with vdeterm, the connection hangs. The bug was that on wirefilter the len parameter on accept was not initialized. As the man page says:

The addrlen argument is a value-result argument: the caller must initialize it to contain the size (in bytes) of the structure pointed to by addr; on return it will contain the actual size of the peer address.

This fix the wirefilter bug. I've also found that this bug was present on vde_router and vde_autolink, so i fix those too.

[rd235]

Thank you.

Given that the variable "addr" has not been used, I think it is simpler and safer to delete the addr and len variables and change the accept statement to
new = accept(fd, &addr, &len);

(this comment applies to the three identical changes).

[rd235]

Thank you for fixing this "ancient" bug....