Describe the bug
Inactive APM Tracer produces invalid spans for OpenTelemetry Tracing bridge. The bug lives inside
go.elastic.co/apm/module/apmotel/v2@v2.4.3/tracer.go:105 in this code:
s.tx = t.provider.apmTracer.StartTransactionOptions(spanName, "", tranOpts) It returns an APM transaction with invalid trace and span ids (all the zero bytes).

To Reproduce
Steps to reproduce the behavior:

1. Use Elastic APM as a bridge to OpenTelemetry API as described here https://www.elastic.co/guide/en/apm/agent/go/current/opentelemetry.html I've taken an existent working ELK Apm instance and have created a tracing provider like it described in the docs.
2. Try to create a new span with the tracer with the code (I've done so in a webserver middleware):

ctx, span := ot.tracer.Start(
	handlerContext.GetContext(),
	serverRequestName(handlerContext.GetHandler()),
)
defer span.End()

3. This span will have invalid trace and span ids. See the screenshot from my debug session as proof.
   

Expected behavior
I suppose that in any case span should have a correct state (or there should be something like Noop span with message details that tracer is not in active state right now).