Handle TLS upgrade errors and log them

Previously the process would just crash and be restarted by its supervisor
silently.
Better error message
Handle processor exits in the reader

N.B. there can be legitimate reasons for processor to exit:
e.g. when it detects missed client heartbeats and must terminate
the connection.
merge bug26282 into stable
merge stable into default
Support the requeue header for NACK frames

GitHub: references #2.
junk bug25958