test_fixed_number_connectors not consitant

[Christian Y. Brenninkmeijer]

Effects Jenkins branch (per change)

https://github.com/SpiNNakerManchester/sPyNNaker8/tree/master/p8_integration_tests/test_fixed_number_connectors

The spike values are still not constant and this is causing failures in Jenkins at times.

Extending the ranges back to VERY large master ones until this addressed to try to get Jenkins green.

[Christian Y. Brenninkmeijer]

Completely reworked tests.
https://github.com/SpiNNakerManchester/sPyNNaker8/blob/jenkins2/unittests/test_using_virtual_board/test_fixed_number_post_connector.py
https://github.com/SpiNNakerManchester/sPyNNaker8/blob/jenkins2/unittests/test_using_virtual_board/test_fixed_number_pre_connector.py

These now check many versions of the connectors produce the correct weights

As under the hood they all work the same on machine virtual tests are enough.