Code review comment for ~info-martin-konrad/epics-base:dont-nuke-global-cac-thread-id-in-exit-handler

Yes, ref. counting would probably be the best way to avoid an exit handler here. I think this could be done with an atomic inc. in ca_context_create() and dec. in ca_context_destroy().

And then I notice that caClientContextIdOnce in access.cpp is already being leaked... So maybe just remove "cacExitHandler()"? This would be far from the only one-time leak in Base.