[k2] extend log file creation timeout to 30 seconds

[PetrShumilov]

Prevent errors like that:

______ ERROR at setup of TestJsonLogsWarnings.test_warning_with_long_env _______
  Traceback (most recent call last):
    File "kphp/tests/python/lib/testcase.py", line 98, in setup_class
      cls.custom_setup()
    File "kphp/tests/python/lib/testcase.py", line 238, in custom_setup
      cls.web_server.start()
    File "kphp/tests/python/lib/k2_server.py", line 46, in start
      super(K2Server, self).start(start_msgs)
    File "kphp/tests/python/lib/web_server.py", line 32, in start
      self._json_log_file_read_fd = open(self._json_log_file, 'r')
  FileNotFoundError: [Errno 2] No such file or directory: 'kphp/tests/python/_tmp/json_logs/artifacts/tmp_test_warnings/17/83/data/log-file'