x86: vmcs lifecycle test

This test VMCLEARs and VMPTRLDs two VMCS's to put each VMCS into different
states of active/not-active and current/not-current and then verifies
that VMREAD/VMWRITE to the current VMCS work correctly.

Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20170421005004.137260-11-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>