hurd: Don't pass FD_CLOEXEC in CMSG_DATA

The flags are used by _hurd_intern_fd, which takes O_* flags, not FD_*.

Also, it is of no concern to the receiving process whether or not
the sender process wants to close its copy of sent file descriptor
upon exec, and it should not influence whether or not the received
file descriptor gets the FD_CLOEXEC flag set in the receiving process.

The latter should in fact be dependent on the MSG_CMSG_CLOEXEC flag
being passed to the recvmsg () call, which is going to be implemented
in the following commit.

Fixes 344e7552
"hurd: Support sending file descriptors over Unix sockets"

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>