x86: xfail some VMX control field tests

When the APIC virtualization address references unbacked memory, kvm
incorrectly fails a VM-entry with "invalid control field(s)." Until
this can be fixed, just skip the VMX control field tests that populate
a VMCS field with a physical address that isn't backed.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>