Fix: race condition when tracing async_nolink processes

[zoevkay]

Description

Discovered a race condition where, when an async_nolink process is started within a transaction, if it finishes after the transaction has completed, the transaction it is linked to no longer exists so the process's results will not be reported.

This PR removes the linking of an async_nolink process to a transaction so that it will consistently be reported to the agent. Note: when using erlang 20, the logging is async and the race condition still exists.

[CLAassistant]

All committers have signed the CLA.

[binaryseed]

Thanks @zoevkay !!

FYI, our thinking behind this is that using async_nolink is signaling that the work done is not part of the current "Transaction", so we aren't going to try tracking it...