event-test: free opaque data when removing callbacks
event-test: free opaque data when removing callbacks

The pure python event loop impl has to call

  libvirt.virEventInvokeFreeCallback

to free the event opaque data from a clean stack context

Signed-off-by: Daniel P. Berrange <bb938cf255e055ff3507f2627d214e8e62118fcf@redhat.com>

libvirt/libvirt-python,libvirt/libvirt-python,libvirt/libvirt-python