Connect.m: When posting messages, kill the scratchpad for each interation
of the posting loop and also killsc at the end. This deals with attempts
to post in a R/O conference which leaves a non-empty scratchpad after
failure to post. 

More work is needed on this code.

There is only one failed task for each blink, regardless of how
many failed postings.
Connect.m: expand the comment in the previous commit.