on-event: add error counter fields to condition

on-event: add error counter fields to condition

Modified from proposed change: don't include error counter index in serdes

The error counter index is an internal implementation detail that
doesn't need to be exposed to the client (the accessor is not reacheble
to them anyway).

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change-Id: Ibc84d4cc3bcc7e304f4b52bd45f1de010dd8b87b