Test assertions should use constant for default sample name

[vreuter]

Right now, a few test assertions use the value of a constant, rather than the constant. If the constant changes, these will likely break. But the test logic is about effect of control flow on the presence of a particular conceptual file, not that the file has a particular name. As such, these test assertions should use string interpolation and the constant (DEFAULT_SAMPLE_NAME) to build the expected filename.

pypiper/tests/pipeline_manager/test_pipeline_manager.py

Lines 104 to 107 in 53850a5

	self._assertFile("sample_pipeline_DEFAULT_SAMPLE_NAME_completed.flag")
	self.pp._set_status_flag("running")
	self._assertNotFile("sample_pipeline_DEFAULT_SAMPLE_NAME_testing.flag")
	self._assertFile("sample_pipeline_DEFAULT_SAMPLE_NAME_running.flag")