BUG/MINOR: add missing modes in proxy_mode_str()

Add the missing PR_MODE_SYSLOG and PR_MODE_PEERS in proxy_mode_str().

Could be backported in every maintained versions.

(cherry picked from commit 06715af9e565c82f39aa157c09d5b9e823490d14)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit e92b1b677024e348f659842389cafa95d35240af)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/src/proxy.c b/src/proxy.c
index 92b84ef..07898b0 100644
--- a/src/proxy.c
+++ b/src/proxy.c
@@ -365,6 +365,10 @@
 		return "http";
 	else if (mode == PR_MODE_CLI)
 		return "cli";
+	else if (mode == PR_MODE_SYSLOG)
+		return "syslog";
+	else if (mode == PR_MODE_PEERS)
+		return "peers";
 	else
 		return "unknown";
 }