Move OBJT_VNODE specific code from vm_object_terminate() to vnode_destroy_vobject().

[kib]

Summary

Peter, could you, please, check this change ?

[jeff]

In general I like this but the double setting of OBJ_DEAD does make it harder to detect things like double frees.

[kib]

Untangle multiple OBJ_DEAD sets.

[kib]

Redo the patch back to the initial variant. Note that there is only one place that calls vm_object_terminate_dead(), so it costs nothing to set OBJ_DEAD flag there and make vm_object_terminate() to expect OBJ_DEAD is already set.

This is cleaner IMO, since both terminate_dead and terminate really not needed.

[pho]

I ran all of the stress2 tests with D21357.61095.diff on amd64. LGTM.