selftests: kvm/set_memory_region_test: do not check RIP if the guest shuts down

On AMD, the state of the VMCB is undefined after a shutdown VMEXIT.  KVM
takes a very conservative approach to that and resets the guest altogether
when that happens.  This causes the set_memory_region_test to fail
because the RIP is 0xfff0 (the reset vector).  Restrict the RIP test
to KVM_EXIT_INTERNAL_ERROR in order to fix this.

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