If the 'cdrom=' option is specified in the definition file but media is

If the 'cdrom=' option is specified in the definition file but media is
not found in the CD drive then main() in vl.c exits and the guest appears
to hang.  This patch modifies vl.c slightly to check for the presents of
media.  If the cdrom cannot be opened then the cd entry is removed from
hd_filename[] and bs_table[] allowing the guest to continue initializing.
If the guest requires the CD media then the guest should report, gracefully
or otherwise, that it's missing.

From: Ross Maxfield <rmaxfiel@novell.com>

Signed-off-by: Keir Fraser <keir@xensource.com>