check for VBAD vnodes on getvnode(). ok andreas@, tedu@ and marius@
check for VBAD vnodes on getvnode(). ok andreas@, tedu@ and marius@

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars