raw-posix: Detect CDROM via ioctl on linux
Current CDROM detection is hardcoded based on source file name.
Make this smarter on linux by attempting a CDROM specific ioctl.
This makes '-cdrom /dev/sr0' succeed with no media present.
v2:
Give ioctl check higher priority than filename check.
v3:
Actually initialize 'prio' variable.
Check for ioctl success rather than absence of specific failure.
v4:
Explicitly mention that change is linux specific.
Signed-off-by: Cole Robinson <crobinso@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>