FreeBSD host physical cdrom fixes

FreeBSD host physical cdrom fixes

This improves physical cdrom support on FreeBSD hosts to be almost as
good as on Linux, with the only notable exception that you still need to
either have the guest itself eject the disc if you want to take it
out/change it, or do a change command in the monitor after taking out
a disc in case a guest cannot eject it itself - otherwise the guest may
continue using state (like size) of the old disc.

Signed-off-by: Juergen Lock <nox@jelal.kn-bremen.de>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6888 c046a42c-6fe2-441c-8c8c-71466251a162