xend: Set close-on-exec flag for datagram sockets

We need to close the socket on the child side when xend creates a
child process such as qemu-dm.

Signed-off-by: Yosuke Iwamatsu <y-iwamatsu@ab.jp.nec.com>

tools/python/xen/web/connection.py

@@ -317,6 +317,8 @@ class SocketDgramListener:
 
     def main(self):
         try:
+            fcntl.fcntl(self.sock.fileno(), fcntl.F_SETFD, fcntl.FD_CLOEXEC)
+
             while True:
                 try:
                     data = self.sock.recv(BUFFER_SIZE)