nodedev: dont rely on ignoring errors on missing properties

nodedev: dont rely on ignoring errors on missing properties

The udevProcessStorage method relies on udevGetIntProperty ignoring
errors about non-existant properties and instead setting the value to
zero. In theory when seeing ID_CDROM=1, you might expect that devices
which are not CDs will get ID_CDROM=0, but that's not what happens in
practice. Instead the property simply won't get set at all.

IOW, the code does not need to care about the value of the property,
merely whether it exists or not.

Reviewed-by: Laine Stump <laine@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>