In my tests for #12354, for some reason ejecting the boot CD like it was done
before this commit immediately halts the machine, as opposed to ejecting the
virtual CD using virt-manager, which does what I expect (triggers emergency
shutdown). So let's go back to ejecting CDs like we did before
commit:62fb8faa, but keep the code
(that's used in another places where /usr/bin/eject would probably not work)
under a different name.