sandbox: support vsock connection to task api

Signed-off-by: Abel Feng <fshb1988@gmail.com>

vendor/github.com/mdlayher/vsock/doc.go

@@ -0,0 +1,10 @@
+// Package vsock provides access to Linux VM sockets (AF_VSOCK) for
+// communication between a hypervisor and its virtual machines.
+//
+// The types in this package implement interfaces provided by package net and
+// may be used in applications that expect a net.Listener or net.Conn.
+//
+//   - *Addr implements net.Addr
+//   - *Conn implements net.Conn
+//   - *Listener implements net.Listener
+package vsock