BUG/MEDIUM: tcpcheck: Add proxy used for healthcheck sections in proxies list

The proxy used to parse healthcheck sections was not inserted in the proxies
list. So its initialization was not properly finalized. Among other things,
it was an issue for some arguments, like regular expressions.

This proxy is now inserted in the proxies list.

This patch should fix the issue #3440. It must be backported to 3.4.

src/tcpcheck.c

@@ -5742,6 +5742,8 @@ int cfg_parse_healthchecks(const char *file, int linenum, char **args, int kwm)
 				err_code |= ERR_ALERT | ERR_FATAL;
 				goto out;
 			}
+			tcpchecks_proxy->next = proxies_list;
+			proxies_list = tcpchecks_proxy;
 		}
 		tcpchecks_proxy->options2 &= ~PR_O2_CHK_ANY;
 		tcpchecks_proxy->tcpcheck.flags = 0;