Fixes regression introduced in ba61160d6c6a69104aa0f68370139d745af11484,
where running check tests with gst-validate-launcher -f would trigger
this exception:
AttributeError: 'GstCheckTest' object has no attribute 'reports'.
Did you mean: 'reporter'?
The member `reports` is meant to be just part of GstValidateTest, but
not other subclasses, even though a usage is still found in the base
class GstTest in the method test_end().
This patch introduces an override of the methods copy() and test_end()
in GstValidateTest so that `reports` is copied and cleared respectively,
but only for validate tests.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5281>
135f859629