Removes duplicate usage of helper_functions

access-node/test/config.py

nest-module/general_config/helper_functions.py

nest-module/general_config/test_config.py

nest-module/test/test_get_multimeters.py

nest-module/test/test_get_neuron_properties.py

nest-module/test/test_get_populations.py

nest-module/test/test_get_simulation_time_info.py

nest-module/test/test_get_spikedetectors.py

nest-module/test/test_kernel_status.py