MINOR: cli: handle EOS/ERROR first

MINOR: cli: handle EOS/ERROR first

It is not especially a bug fixed. But APPCTX_FL_EOS and APPCTX_FL_ERROR
flags must be handled first. These flags are set by the applet itself and
should mark the end of all processing. So there is not reason to get the
output buffer in first place.

This patch could be backported as far as 3.0.

(cherry picked from commit fb7665552668df368bbc85ef56beca11c356f53a)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 9a874dc54c3a6eb061f19d0a65e882d17d4b1a3e)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>