attach: use move_fd in lxc_proc_close_ns_fd
attach: use move_fd in lxc_proc_close_ns_fd

Previously this set `ctx->ns_fd[*]` to `-EBADF` until commit
fd2a88b190eb ("attach: cleanup macros lxc_proc_close_ns_fd",
but there are some code paths where we call this before
later calling `lxc_proc_put_context_info` which would call
this function again with the file descriptors still
unchanged.

Signed-off-by: Wolfgang Bumiller <bac7898f539fd233d9ce33be7a9eda13ee647930@proxmox.com>

ss1h2a3tw/lxc,ss1h2a3tw/lxc,ss1h2a3tw/lxc,hallyn/lxc,hallyn/lxc,hallyn/lxc