Update to use go modules (#671)

This includes updates to CI config, vendor files, etc.
I've hard-coded the k8s depedency at 1.13.4 to keep it inline with what
we currently have and to make sure a another run of `go mod tidy`
doesn't accidentally update it to an unexpected version.

Thanks to hectorj2f for carrying this along.

vendor/golang.org/x/sys/unix/syscall_bsd.go

@@ -206,7 +206,7 @@ func (sa *SockaddrDatalink) sockaddr() (unsafe.Pointer, _Socklen, error) {
 	return unsafe.Pointer(&sa.raw), SizeofSockaddrDatalink, nil
 }
 
-func anyToSockaddr(rsa *RawSockaddrAny) (Sockaddr, error) {
+func anyToSockaddr(fd int, rsa *RawSockaddrAny) (Sockaddr, error) {
 	switch rsa.Addr.Family {
 	case AF_LINK:
 		pp := (*RawSockaddrDatalink)(unsafe.Pointer(rsa))
@@ -286,7 +286,7 @@ func Accept(fd int) (nfd int, sa Sockaddr, err error) {
 		Close(nfd)
 		return 0, nil, ECONNABORTED
 	}
-	sa, err = anyToSockaddr(&rsa)
+	sa, err = anyToSockaddr(fd, &rsa)
 	if err != nil {
 		Close(nfd)
 		nfd = 0
@@ -306,7 +306,7 @@ func Getsockname(fd int) (sa Sockaddr, err error) {
 		rsa.Addr.Family = AF_UNIX
 		rsa.Addr.Len = SizeofSockaddrUnix
 	}
-	return anyToSockaddr(&rsa)
+	return anyToSockaddr(fd, &rsa)
 }
 
 //sysnb socketpair(domain int, typ int, proto int, fd *[2]int32) (err error)
@@ -356,7 +356,7 @@ func Recvmsg(fd int, p, oob []byte, flags int) (n, oobn int, recvflags int, from
 	recvflags = int(msg.Flags)
 	// source address is only specified if the socket is unconnected
 	if rsa.Addr.Family != AF_UNSPEC {
-		from, err = anyToSockaddr(&rsa)
+		from, err = anyToSockaddr(fd, &rsa)
 	}
 	return
 }