Add cpbuild to OmeroCpp/.gitignore
Remove errant cout
cmdcallbacktest: attempt to fix BSD runs
c++/units: attempt to fix symbol map errors
c++/units: also remove '::Units' from model test
c++/tests: enhance check and add to on cancel

The check previously added to assertFinished
is also needed on assertCancelled. But rather
than accepting any non-0 finished count as
being exceptional, only retry the poll if it's
0, meaning that no response was received at all.
Add catch to get line/file of error

It's unclear why we're currently getting a
ConnectionLostException. Locally (calling
to trout) I can't reproduce.
Merge pull request #3247 from joshmoore/cpp-green-2

C++ green 2