Fix bad time unit types in wait_for_namespace_active (#212)

See
#203 (review)

Error sample:
```pytb
I1030 12:10:45.628975 140704582733824 k8s.py:1302] Waiting for namespace stk-server-ns-wait to become active
Traceback (most recent call last):
  File "/Users/sergiitk/Development/psm-interop/bin/run_test_server.py", line 166, in <module>
    app.run(main)
  File "/Users/sergiitk/Development/psm-interop/venv/lib/python3.10/site-packages/absl/app.py", line 308, in run
    _run_main(main, args)
  File "/Users/sergiitk/Development/psm-interop/venv/lib/python3.10/site-packages/absl/app.py", line 254, in _run_main
    sys.exit(main(argv))
  File "/Users/sergiitk/Development/psm-interop/bin/run_test_server.py", line 152, in main
    server_runner.run(**run_kwargs)
  File "/Users/sergiitk/Development/psm-interop/framework/test_app/runners/k8s/k8s_xds_server_runner.py", line 216, in run
    super().run()
  File "/Users/sergiitk/Development/psm-interop/framework/test_app/runners/k8s/k8s_base_runner.py", line 199, in run
    self.k8s_namespace.wait_for_namespace_active()
  File "/Users/sergiitk/Development/psm-interop/framework/infrastructure/k8s.py", line 1303, in wait_for_namespace_active
    retryer = retryers.constant_retryer(
  File "/Users/sergiitk/Development/psm-interop/framework/helpers/retryers.py", line 115, in constant_retryer
    stops.append(stop.stop_after_delay(timeout.total_seconds()))
AttributeError: 'int' object has no attribute 'total_seconds'
```

Author: sergiitk

framework/infrastructure/k8s.py

@@ -1296,8 +1296,8 @@ def _namespace_active(cls, namespace: V1Namespace) -> bool:
 
     def wait_for_namespace_active(
         self,
-        timeout: _timedelta = WAIT_SHORT_TIMEOUT_SEC,
-        retry_wait: _timedelta = WAIT_SHORT_SLEEP_SEC,
+        timeout: _timedelta = WAIT_SHORT_TIMEOUT,
+        retry_wait: _timedelta = WAIT_SHORT_SLEEP,
     ) -> None:
         logger.info("Waiting for namespace %s to become active", self.name)
         retryer = retryers.constant_retryer(