MINOR: config: Alert about extra arguments for errorfile and errorloc

MINOR: config: Alert about extra arguments for errorfile and errorloc

errorfile and errorloc directives expect excatly two arguments. But extra
arguments were just ignored while an error should be emitted. It is now
fixed.

This patch could be backported as far as 2.2 if necessary.

(cherry picked from commit f578811c4e8965f243cd16a6f569909a2a07498c)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 03d6c648dfc3ab364149aa747c1574c847526193)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>