BUG/MINOR: proxy: fix check_{command,path} leak on deinit()

proxy check_{command,path} members (used for "external-check" feature)
weren't cleaned up in free_proxy(), resulting in small memory leak if
"external-check command" or "external-check path" were used on a regular
or default proxy.

It may be backported to all stable versions.

src/proxy.c

@@ -219,6 +219,8 @@ void free_proxy(struct proxy *p)
 	free(p->capture_name);
 	istfree(&p->monitor_uri);
 	istfree(&p->server_id_hdr_name);
+	ha_free(&p->check_command);
+	ha_free(&p->check_path);
 	free(p->rdp_cookie_name);
 	free_email_alert(p);
 	free(p->invalid_rep);