x86: VMX: test MTF VM-exit event injection

SDM 26.6.2 describes how the VM-entry interruption-information field
may be configured to inject an MTF VM-exit upon VM-entry. Ensure that an
MTF VM-exit occurs when the VM-entry interruption-information field is
configured appropriately by the host.

Signed-off-by: Oliver Upton <oupton@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Peter <Shier&lt;pshier@google.com>
Message-Id: <20200414214634.126508-2-oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>