The setting is used by the rate limit checks. However, those tests are
designed to check for handling the rate limit only. The outstanding
requests limits is not checked and hitting it interferes with the rate
limit check, leading to spurious failure.

Raise the value to a limit that it will no longer affect the rate
limit tests.

The session process can not get an `EXIT` event from the owner since
it is never linked to it. This is a left over from very ancient
version of the session logic. Removed.

Include the session information in the log for a `DOWN` event.

* change logs to lebel debug that where intendet for debugging only,
  but where not using the debug level
* remove obsolete debug logs
* clarify some non-debug logs

A reference count underflow indicates a logic bug in the reference
counting logic. Log it with proper criticallity, but otherwise try to
continue.