nested vmx: use VMREAD/VMWRITE to construct vVMCS if enabled VMCS shadowing

nested vmx: use VMREAD/VMWRITE to construct vVMCS if enabled VMCS shadowing

Before the VMCS shadowing feature, we use memory operation to build up
the virtual VMCS. This does work since this virtual VMCS will never be
loaded into real hardware. However after we introduce the VMCS
shadowing feature, this VMCS will be loaded into hardware, which
requires all fields in the VMCS accessed by VMREAD/VMWRITE.

Besides, the virtual VMCS revision identifer should also meet the
hardware's requirement, instead of using a faked one.

Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
Acked-by Eddie Dong <eddie.dong@intel.com>
Committed-by: Jan Beulich <jbeulich@suse.com>