ringbuf: fix temporary file creation
ringbuf: fix temporary file creation

lxc_make_tmpfile() uses mkstemp() internally, and thus expects the
template to contain 'XXXXXX' and be writable.

Signed-off-by: Thomas Moschny <f95dacb889f09635eade811e4aa84598d1702075@gmx.de>
Signed-off-by: Christian Brauner <48455ab3070520a2d174545c7239d6d0fabd9a83@ubuntu.com>

ss1h2a3tw/lxc,ss1h2a3tw/lxc,caglar10ur/lxc,caglar10ur/lxc,caglar10ur/lxc,hallyn/lxc,hallyn/lxc,hallyn/lxc,ss1h2a3tw/lxc