hvm, ioemu: Fix the ide/cdrom emulation error on FC7 guest.

hvm, ioemu: Fix the ide/cdrom emulation error on FC7 guest.

The new libata-eh in the Linux kernel is throwing a fit over the QEMU
cdrom device for two reasons:

1) DRQ can be set with ERR_STAT set.  This is a violation of the ATAPI
state machine.

2) After a TEST_UNIT_READY ATAPI command is sent ERR_STAT is getting
   set
which is correct.  But, when the OS issues another ATAPI command
ERR_STAT is still set.  Which is bad since the next expected command
from the OS is REQUEST_SENSE to find out why ERR_STAT is set.

bug this fixes: https://bugzilla.novell.com/show_bug.cgi?id=3D291775

Signed-off-by: Brandon Philips <bphilips@suse.de>
Porting this qemu fix to xen.

Signed-off-by: Xu Dongxiao <dongxiao.xu@intel.com>