[PSM Interop] Change the log message from Client pods to Client container (#34029)

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diff --git a/tools/run_tests/xds_k8s_test_driver/framework/xds_k8s_testcase.py b/tools/run_tests/xds_k8s_test_driver/framework/xds_k8s_testcase.py
index bf8e312..bae651a 100644
--- a/tools/run_tests/xds_k8s_test_driver/framework/xds_k8s_testcase.py
+++ b/tools/run_tests/xds_k8s_test_driver/framework/xds_k8s_testcase.py
@@ -670,7 +670,7 @@
                 client_restarts,
                 0,
                 msg=(
-                    "Client pods unexpectedly restarted"
+                    "Client container unexpectedly restarted"
                     f" {client_restarts} times during test. In most cases, this"
                     " is caused by the test client app crash."
                 ),
@@ -679,7 +679,7 @@
                 server_restarts,
                 0,
                 msg=(
-                    "Server pods unexpectedly restarted"
+                    "Server container unexpectedly restarted"
                     f" {server_restarts} times during test. In most cases, this"
                     " is caused by the test client app crash."
                 ),
diff --git a/tools/run_tests/xds_k8s_test_driver/framework/xds_url_map_testcase.py b/tools/run_tests/xds_k8s_test_driver/framework/xds_url_map_testcase.py
index efa513c..6fa1c1d 100644
--- a/tools/run_tests/xds_k8s_test_driver/framework/xds_url_map_testcase.py
+++ b/tools/run_tests/xds_k8s_test_driver/framework/xds_url_map_testcase.py
@@ -436,7 +436,7 @@
 
             # Fail if any of the pods restarted.
             error_msg = (
-                "Client pods unexpectedly restarted"
+                "Client container unexpectedly restarted"
                 f" {client_restarts} times during test."
                 " In most cases, this is caused by the test client app crash."
             )