KVM: selftests: Rename vm_create_without_vcpus() => vm_create()

Rename vm_create_without_vcpus() to vm_create() so that it's not
misconstrued as helper that creates a VM that can never have vCPUs, as
opposed to a helper that "just" creates a VM without vCPUs added at time
zero.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>