Test step fragment "Validate flight sharing" does not skip test when required to

[mickmis]

Describe the bug
Test step fragment described by validate_shared_operational_intent.md is supposed to interrupt its execution and skip the test step fragment when a new or modified operational intent is not found, but only if that is explicitly allowed by the test scenario.

In scenarios/astm/utm/test_steps.py the recent PR #376 extracted some logic out of expect_shared into _operational_intent_shared_check. Previously the returns would interrupt the execution of the flow because they were in expect_shared, but now they are not and they do not interrupt the execution anymore:

monitoring/monitoring/uss_qualifier/scenarios/astm/utm/test_steps.py

Lines 359 to 364 in d9c8ea8

	self._scenario.record_note(
	f"{self._flight_planner.participant_id} skipped step",
	f"No new operational intent was found in DSS, instructed to skip test step '{self._test_step}'.",
	)
	self._scenario.end_test_step()
	return None

monitoring/monitoring/uss_qualifier/scenarios/astm/utm/test_steps.py

Lines 414 to 419 in d9c8ea8

	self._scenario.record_note(
	f"{self._flight_planner.participant_id} skipped step",
	f"Operational intent reference with ID {self._orig_oi_ref.id} not found in DSS, instructed to skip test step '{self._test_step}'.",
	)
	self._scenario.end_test_step()
	return None

Possible solution
Interrupt execution in callers of _operational_intent_shared_check