Fix F_DUPFD_CLOEXEC operation args

The F_DUPFD_CLOEXEC operation with fcntl() expects a single
int argument, specifying the minimum FD number for the newly
dup'd file descriptor. We were not specifying that causing
random stack data to be accessed as the FD number. Sometimes
that worked, sometimes it didn't.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>
(cherry picked from commit d6670a64)

src/rpc/virnetsocket.c

@@ -1055,7 +1055,7 @@ int virNetSocketDupFD(virNetSocketPtr sock, bool cloexec)
     int fd;
 
     if (cloexec)
-        fd = fcntl(sock->fd, F_DUPFD_CLOEXEC);
+        fd = fcntl(sock->fd, F_DUPFD_CLOEXEC, 0);
     else
         fd = dup(sock->fd);
     if (fd < 0) {