Fix linking with newrelic.distributed_tracing_enabled=1

[ostrolucky]

There are several behavioural differences with newrelic.distributed_tracing_enabled=1 that this patch addresses

1. newrelic_add_custom_parameter('traceId', $value); hack does not work. Traces do not get traceId matching $value assigned
2. As an obvious solution, custom TraceIdFactory which uses newrelic_get_trace_metadata instead of UUIDs presents itself. However, this also does not work, because:
3. Transaction ID apparently might change at any point of time during the request. Specifically, I've observed newrelic_name_transaction changes this ID.

This bundle in sequence:

1. creates TraceID at beginning of request
2. calls newrelic_name_transaction
3. calls newrelic_add_custom_parameter('traceId', $this->traceId->__toString());

This doesn't work, because step 3 uses ID generated at step 1, but NR changed ID in step 2, hence Logs get different trace.id assigned than NR Transaction has.

This could be solved by custom NewrelicNativeTraceIdFactory + calling $this->traceId->refresh() right after $this->interactor->setApplicationName( but I worry that this might work in this case, but there will be other cases where NR extension changes current traceId.

Hence, I think solution in this commit is quite robust and will work with both states of newrelic.distributed_tracing_enabled out of the box. Only disadvantage is that if users have newrelic.distributed_tracing_enabled=1, even if they define custom traceIdFactory, "native" NR transaction ID will be used despite whatever they generate in their custom factory. However, I believe this is OK, because whatever they generate in their custom factory wouldn't be taken over by NR extension anyways, because of very first point mentioned in this commit message