Race condition callee sends request immediately after a response

[psanders]

Describe the bug
The edgeport module has a race condition that causes the serverTransaction to be overwritten before the response is received. This causes the error "javax.sip.SipException: Response does not belong to this transaction." to be thrown, and the message flow breaks.

To Reproduce
Using SEET, create a flow scenario where the callee sends a request immediately after a response. Observe the edgeport module throwing a "javax.sip.SipException: Response does not belong to this transaction." error.

Expected behavior
The edgeport module should handle this scenario without an error.

System information (please complete the following):
NA

Additional context
Tracing the error, I found that the error gets thrown here.