Check debug messages during blocking RFC call

[tolauwae]

For PR #238 we allowed checking debug messages during blocking RFC calls.

There is an issue with the supervisor and the proxy RFC calls. Because they are synchronous, they hijack the main interpretation loop. The loop does not advance as it waits for the proxy call to finish, this is inline with our "atomic" design of primitives, no debug messages are processed during their execution.

In this case we do want this, since during the proxy call, the proxy device will send back debug messages.

This was changed in 34b89fd.

Problem: However, we might not want to process just any debug message. What if we send a RUN command? This would break everything catastrophically.