[MINOR] acl: add srv_conn acl to count connections on a
specific backend server

These ACLs are used to check the number of active connections on the specified server in the specified backend.
diff --git a/src/acl.c b/src/acl.c
index 26b82cb..9d9a746 100644
--- a/src/acl.c
+++ b/src/acl.c
@@ -1732,7 +1732,8 @@
 
 	list_for_each_entry(acl, &p->acl, list) {
 		list_for_each_entry(expr, &acl->expr, list) {
-			if (strcmp(expr->kw->kw, "srv_is_up") == 0) {
+			if (strcmp(expr->kw->kw, "srv_is_up") == 0 ||
+			    strcmp(expr->kw->kw, "srv_conn") == 0) {
 				struct proxy *px;
 				struct server *srv;
 				char *pname, *sname;