Carve out portion of vm_create_default so that selftests can modify
a "default" VM prior to creating vcpus.
Signed-off-by: NDavid Dunn <daviddunn@google.com>
Message-Id: <20220223225743.2703915-3-daviddunn@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>