CI: ensure clean iperf3 server startup by killing existing processes on same port

Before starting a new iperf3 server instance in CI tests, explicitly kill any existing
iperf3 processes bound to the same port. This prevents conflicts or failures caused by
leftover iperf3 servers from previous runs that did not terminate properly or on time.
The cleanup is performed using `pkill` before launching the new server.

ci-scripts/cls_oaicitest.py

@@ -503,6 +503,11 @@ class OaiCiTest():
 			t = iperf_time * 2.5
 			cmd_ue.run(f'rm {client_filename}', reportNonZero=False, silent=True)
 			if cn.runIperf3Server():
+				# Clean up any existing iperf3 server processes on this port.
+				ret = cmd_svr.run(f"{cn.getCmdPrefix()} pkill -f '.*iperf3.*{port}'", reportNonZero=False)
+				# If pkill succeeds, it means there was a leftover iperf3 server.
+				if ret.returncode == 0:
+					logging.warning(f'Iperf3 server on port {port} detected and terminated')
 				cmd_svr.run(f'{cn.getCmdPrefix()} timeout -vk3 {t} iperf3 -s -B {svrIP} -p {port} -1 {jsonReport} >> /dev/null &', timeout=t)
 			cmd_ue.run(f'{ue.getCmdPrefix()} timeout -vk3 {t} {iperf_ue} -B {ueIP} -c {svrIP} -p {port} {iperf_opt} {jsonReport} {serverReport} -O 5 >> {client_filename}', timeout=t)
 			dest_filename = archiveArtifact(cmd_ue, ctx, client_filename)