vbox: Remove VBOX_OBJECT_CHECK macro

vbox: Remove VBOX_OBJECT_CHECK macro

We should follow the rules that CHECK macro only do checking works.
But this VBOX_OBJECT_CHECK and VBOX_OBJECT_HOST_CHECK declared some
varibles at the same time, which broke the rule. So the patch
removed this macros and dispatched it in source code.

The storage driver is still not rewriten at this point. So, I
remains the VBOX_OBJECT_CHECK macro in vbox_tmpl.c. But this will
finally be removed in patch 'vbox: Remove unused things in vbox_tmpl.c'