labs: pass vm_name as arg to _vbox_configure_ifs

_vbox_configure_ifs should no longer use the environment variable
NODE_NAME as the name of the node VM. It gets replaced by the correct
value passed as an argument.

Change-Id: I9d36420bcf56bbabe2f47cee2d7eb2ad824bf5d1
Merge "labs: pass vm_name as arg to _vbox_configure_ifs"