Fix TypeError of non-dict response data from Agent announcement.

[pvital]

This PR fixes the TypeError of non-dict response data from Agent announcement.

tests/clients/kafka/test_confluent_kafka.py::TestConfluentKafka::test_trace_confluent_kafka_produce
  /root/repo/venv/lib/python3.12/site-packages/_pytest/threadexception.py:82: PytestUnhandledThreadExceptionWarning: Exception in thread Instana Machine
  
  Traceback (most recent call last):
    File "/usr/local/lib/python3.12/threading.py", line 1075, in _bootstrap_inner
      self.run()
    File "/usr/local/lib/python3.12/threading.py", line 1433, in run
      self.function(*self.args, **self.kwargs)
    File "/root/repo/venv/lib/python3.12/site-packages/fysom/__init__.py", line 315, in fn
      self.transition()
    File "/root/repo/venv/lib/python3.12/site-packages/fysom/__init__.py", line 310, in _tran
      self._after_event(e)
    File "/root/repo/venv/lib/python3.12/site-packages/fysom/__init__.py", line 342, in _after_event
      return getattr(self, fnname)(e)
             ^^^^^^^^^^^^^^^^^^^^^^^^
    File "/root/repo/venv/lib/python3.12/site-packages/fysom/__init__.py", line 99, in _callback
      return func(obj, *args, **kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "/root/repo/src/instana/fsm.py", line 95, in lookup_agent_host
      self.fsm.announce()
    File "/root/repo/venv/lib/python3.12/site-packages/fysom/__init__.py", line 315, in fn
      self.transition()
    File "/root/repo/venv/lib/python3.12/site-packages/fysom/__init__.py", line 310, in _tran
      self._after_event(e)
    File "/root/repo/venv/lib/python3.12/site-packages/fysom/__init__.py", line 342, in _after_event
      return getattr(self, fnname)(e)
             ^^^^^^^^^^^^^^^^^^^^^^^^
    File "/root/repo/venv/lib/python3.12/site-packages/fysom/__init__.py", line 99, in _callback
      return func(obj, *args, **kwargs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "/root/repo/src/instana/fsm.py", line 163, in announce_sensor
      self.agent.set_from(payload)
    File "/root/repo/src/instana/agent/host.py", line 136, in set_from
      self.options.set_from(res_data)
    File "/root/repo/src/instana/options.py", line 142, in set_from
      if "secrets" in res_data:
         ^^^^^^^^^^^^^^^^^^^^^
  TypeError: argument of type 'bool' is not iterable

https://app.circleci.com/pipelines/github/instana/python-sensor/3917/workflows/5df45e12-c567-4688-82af-9a0f51f72bd4/jobs/29635?invite=true#step-104-6215_80

[CagriYonca]

Looks good to me!