Ensure example_finished gets reported from context-hook failures

Created by: jenseng

Regression in c0564a39

#reporter is a RSpec::Core::NullReporter at this point, so pass along the correct reporter argument.

It appears that #reporter is never actually used in rspec-core (or anywhere?), and given that we rely on a reporter argument it feels a bit error prone. Perhaps #reporter should just be removed? Alternatively, maybe we should stop passing reporter around internally and just set @reporter in places like fail_with_exception?

Feels out of scope for this bugfix, but I think it warrants discussing.