pre-dump: avoid sleeping in the open() syscall

For example opening the FIFO blocks until the other end is opened also.

We can use O_PATH to avoid sleeping in the open() call.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

files.c

@@ -416,7 +416,7 @@ static int predump_one_fd(int pid, int fd)
 	 * enightened version without fds draining.
 	 */
 
-	lfd = open_proc(pid, "fd/%d", fd);
+	lfd = __open_proc(pid, O_PATH | O_RDONLY, "fd/%d", fd);
 	if (lfd < 0)
 		return 0; /* That's OK, it can be a socket */