Fix InstanceActionEvent traceback parameter not serializable

The change to use InstanceActionEvent in compute.utils.EventReporter
changed the order of how things are done. Before, traceback info were
converted to a string before being sent to the conductor. Now, since
the object method being used remotes itself, the order becomes the
opposite and any captured tracebacks are sent as is, resulting in
errors during messaging.

This bug has actually existed in the now used methods all time, the
methods have just not been used up until now. When looking into this
issue, it was uncovered that tests for the entire class was not
running (presumable a mistake). This change updates these tests to be
inline with recent changes and makes sure they actually run.

Change-Id: Ibedddd606b9d25ffbbb2b1b5358cf0aa4741083f
Closes-Bug: #1317804