MEDIUM: cli: Use the sedesc to report and detect end of processing

MEDIUM: cli: Use the sedesc to report and detect end of processing

It is the same kind of change than for the cache applet. Idea is to use the SE
desc instead of the channel or the SC to report end-of-input, end-of-stream and
errors.

Truncated commands are now reported on error. Other changes are the same than
for the cache applet. We now set SE_FL_EOS flag instead of calling cf_shutr()
and calls to cf_shutw are removed.