Bugfix/fix gs2 diagnostics new unit test

• Ensure python script has a suitable shebang

• Set force_maxwell_reinit false to ensure restarted job values match perfectly

• Ensure the heating diagnostic is correctly enabled in new diagnostic runs

• Make variable comparison use np.allclose rather than checking for exact equality

  This is motivated by the fact that we compare variables which are derived from "raw" information but these calculations may incur different floating round off error.

Currently this test is not actually taking place in next. This is fixed by PR #347 , which currently fails due to the absence of these fixes to the test.