test coverage cleanup

- dataman clean exit code
 - unit test proper cleanup
 - add some level of simulated sensors for tests
 - delete unused test/standard_vtol

src/modules/dataman/dataman.c

@@ -1275,5 +1275,5 @@ dataman_main(int argc, char *argv[])
 		return -1;
 	}
 
-	return 1;
+	return 0;
 }