kvm: selftests: add svm nested shutdown test

Add test that tests that on SVM if L1 doesn't intercept SHUTDOWN,
then L2 crashes L1 and doesn't crash L2

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20221103141351.50662-7-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>