Iperf3: connection is getting closed from the client side unexpectedly

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# Context
iperf3 commands are failing with the following error: `the client has unexpectedly closed the connection`.
* Version of iperf3: 3.17.1

* Hardware:

* Operating system (and distribution, if any): Azure Linux/CBL-Mariner and SUSE Linux

_Please note: iperf3 is supported on Linux, FreeBSD, and macOS.
Support may be provided on a best-effort basis to other UNIX-like
platforms. We cannot provide support for building and/or running
iperf3 on Windows, iOS, or Android._

* Other relevant information (for example, non-default compilers,
libraries, cross-compiling, etc.):

_Please fill out one of the "Bug Report" or "Enhancement Request"
sections, as appropriate. Note that submissions of bug fixes, new
features, etc. should be done as a pull request at
https://github.com/esnet/iperf/pulls_

# Bug Report

* Expected Behavior
The lisa test case [perf_udp_iperf_sriov](https://github.com/microsoft/lisa/blob/d97439f4afe688a4e410b3090ab0dac3b09c5da1/microsoft/testsuites/performance/networkperf.py#L281) uses iperf3 to test the network throughput between 2 Azure Linux VMs. This test should pass for Azure Linux VMs.
* Actual Behavior
The test is intermittently failing with the following error - `error: the client has unexpectedly closed the connection`.
* Steps to Reproduce
-- Spin up 8 iperf servers at the same time in parallel (we are using port 750-757 here) - `sudo iperf3 -s -1 -J -i10 -f g -p `
-- Now run 8 clients in parallel with the following parameters - `sudo iperf3 -t 10 -c -u -J -i1 -f g -p -P 64 -l 8192 -4`

When these commands run for the last port (757 in this case) the error occurs.
* Possible Solution

# Enhancement Request

* Current behavior

* Desired behavior

* Implementation notes

Start with the linked LISA test case, perf_udp_iperf_sriov in networkperf.py, and reproduce the parallel server and client commands using eight ports and -P 64. Trace the intermittent client-side closure in iperf3's connection and UDP parallel-stream handling. Done means identifying the failure cause, adding coverage where appropriate, and confirming the test no longer fails intermittently.

Written by the indexing model from the issue text.