No support for double nested 64 bit guest using VCDriver

64bit instances launched on ESX via the VCDriver will not
support running 64bit guests. There is an option that can
be passed during the vmx creation that will allow for this
to happen. This is very useful if you want to run hypervisors
 (esx, kvm) on top of ESX and then run 64bit VMs on top of
those hypervisors.

Fixes bug 1192256

Change-Id: Id6eb224c97569737cbb41f1b64f61805e1df004e