BUG/MINOR: cli: wait for payload data even without prompt

BUG/MINOR: cli: wait for payload data even without prompt

During a payload transfer, we need to wait for the data even when we are
not in interactive mode. Indeed, the data could be received line per
line progressively instead of in one recv.

Previously the CLI was doing a SHUTW just after the first line if it was
not in interactive mode. We now check if we are in payload mode to do
a SHUTW.

Should be backported in 1.8.