vm-virtio: vhost_user: block: On shutdown() drop the socket

This causes the vhost-user-block backend to shutdown.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

vm-virtio/src/vhost_user/blk.rs

@@ -14,6 +14,7 @@ use libc::EFD_NONBLOCK;
 use std::cmp;
 use std::io::Write;
 use std::mem;
+use std::os::unix::io::AsRawFd;
 use std::result;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::Arc;
@@ -314,6 +315,10 @@ impl VirtioDevice for Blk {
             self.queue_evts.take().unwrap(),
         ))
     }
+
+    fn shutdown(&mut self) {
+        let _ = unsafe { libc::close(self.vhost_user_blk.as_raw_fd()) };
+    }
 }
 
 virtio_pausable!(Blk);