BUG/MINOR: http-htx: Handle warnings when parsing http-error and http-errors

First of all, this patch is tagged as a bug. But in fact, it only fixes a bug in
the 2.2. On the 2.3 and above, it only add the ability to display warnings, when
an http-error directive is parsed from a proxy section and when an errorfile
directive is parsed from a http-errors section.

But on the 2.2, it make sure to display the warning emitted on a content-length
mismatch when an errorfile is parsed. The following is only applicable to the
2.2.

commit "BUG/MINOR: http-htx: Just warn if payload of an errorfile doesn't match
the C-L" (which is only present in 2.2, 2.1 and 2.0 trees, i.e see commit
7bf3d81d3cf4b9f4587 in 2.2 tree), is changing the behavior of `http_str_to_htx`
function. It may now emit warnings. And, it is the caller responsibility to
display it.

But the warning is missing when an 'http-error' directive is parsed from
a proxy section. It is also missing when an 'errorfile' directive is
parsed from a http-errors section.

This bug only exists on the 2.2. On earlier versions, these directives
are not supported and on later ones, an error is triggered instead of a
warning.

Thanks to William Dauchy that spotted the bug.

This patch must be backported as far as 2.2.

(cherry picked from commit 3005d28eb825f700820a8d38d6d7fa6ab51a1f80)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/src/http_htx.c b/src/http_htx.c
index ed49319..ee1bfd3 100644
--- a/src/http_htx.c
+++ b/src/http_htx.c
@@ -1987,6 +1987,9 @@
 	conf_err->line = line;
 	LIST_ADDQ(&curpx->conf.errors, &conf_err->list);
 
+	/* handle warning message */
+	if (*errmsg)
+		ret = 1;
   out:
 	return ret;
 
@@ -2200,6 +2203,10 @@
 			err_code |= ERR_ALERT | ERR_FATAL;
 			goto out;
 		}
+		if (errmsg) {
+			ha_warning("parsing [%s:%d] : %s: %s\n", file, linenum, args[0], errmsg);
+			err_code |= ERR_WARN;
+		}
 
 		reply = calloc(1, sizeof(*reply));
 		if (!reply) {