Change the check for /livecd when booting a CD to check for a file called livecd...

Change the check for /livecd when booting a CD to check for a file called livecd, rather than just the existence of /livecd, which should keep it from finding disks with a /livecd directory.

git-svn-id: svn+ssh://svn.gentoo.org/var/svnroot/genkernel/trunk@513 67a159dc-881f-0410-a524-ba9dfbe2cb84