Only decache guest CR3 value if vcpu->arch.cr3 is stale.
Fixes loadvm with live guest.
Signed-off-by: NMarcelo Tosatti <mtosatti@redhat.com>
Tested-by: NMarkus Schade <markus.schade@gmail.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>