Use report_test_failure in TensorFlow easyblock

[Flamefire]

Also make use of the new function in the TF easyblock to avoid calling a costly exception and the superflous log entry created by that.

Also avoids the issue which is generically fixed in #2516

Requires framework bugfix easybuilders/easybuild-framework#3782

[Flamefire]

Test report by @Flamefire

Overview of tested easyconfigs (in order)

• **FAIL (unhandled exception: 'EB_TensorFlow' object has no attribute 'ignore_test_failure')Traceback (most recent call last):
  File "/home/h3/s3248973/.local/EasyBuildDev/easybuild-framework/easybuild/main.py", line 118, in build_and_install_software
  (ec_res['success'], app_log, err) = build_and_install_one(ec, init_env)
  File "/home/s3248973/.local/EasyBuildDev/easybuild-framework/easybuild/framework/easyblock.py", line 3697, in build_and_install_one
  result = app.run_all_steps(run_test_cases=run_test_cases)
  File "/home/s3248973/.local/EasyBuildDev/easybuild-framework/easybuild/framework/easyblock.py", line 3585, in run_all_steps
  self.run_step(step_name, step_methods)
  File "/home/s3248973/.local/EasyBuildDev/easybuild-framework/easybuild/framework/easyblock.py", line 3438, in run_step
  step_method(self)()
  File "/home/s3248973/.local/EasyBuildDev/easybuild-easyblocks/easybuild/easyblocks/generic/pythonbundle.py", line 128, in extensions_step
  super(PythonBundle, self).extensions_step(*args, **kwargs)
  File "/home/s3248973/.local/EasyBuildDev/easybuild-framework/easybuild/framework/easyblock.py", line 2439, in extensions_step
  txt = ext.run()
  File "/home/s3248973/.local/EasyBuildDev/easybuild-easyblocks/easybuild/easyblocks/generic/pythonpackage.py", line 754, in run
  step_method(self)()
  File "/tmp/easybuild-tmp/included-easyblocks-hynIgB/easybuild/easyblocks/tensorflow.py", line 977, in test_step
  self.report_test_failure(fail_msg)
  File "/home/s3248973/.local/EasyBuildDev/easybuild-framework/easybuild/framework/easyblock.py", line 1834, in report_test_failure
  if self.ignore_test_failure:
  AttributeError: 'EB_TensorFlow' object has no attribute 'ignore_test_failure'
  ** TensorFlow-2.5.0-fosscuda-2019b-Python-3.7.4.eb

Build succeeded for 0 out of 1 (1 easyconfigs in total)
taurusa4 - Linux centos linux 7.7.1908, x86_64, Intel(R) Xeon(R) CPU E5-2603 v4 @ 1.70GHz (broadwell), Python 2.7.5
See https://gist.github.com/80357d4dd84eb865b1f48705a6debc9a for a full test report.

[Flamefire]

Test report by @Flamefire

Overview of tested easyconfigs (in order)

• SUCCESS TensorFlow-2.5.0-fosscuda-2019b-Python-3.7.4.eb

Build succeeded for 1 out of 1 (1 easyconfigs in total)
taurusa4 - Linux centos linux 7.7.1908, x86_64, Intel(R) Xeon(R) CPU E5-2603 v4 @ 1.70GHz (broadwell), Python 2.7.5
See https://gist.github.com/695fbe9ca14bb9a59d571e5c5c5813b9 for a full test report.