BUG/MEDIUM: server: clear dynamic srv on delete from proxy id/name trees

Do not leave deleted server in used_server_id/used_server_addr backend
trees. This might lead to crashes if a deleted server is used through
these trees.

At this moment, dynamic servers are only added in used_server_id if they
have a fixed id. They are never inserted in used_server_addr as this
code is missing. So these new delete instructions are noop. However, a
fix will be provided soon to insert properly all dynamic servers in both
used_server_id and used_server_addr trees so the deletion counterpart
will be mandatory in the CLI server delete handler.

This must be backported to 2.4.
diff --git a/src/server.c b/src/server.c
index 14f5485..20121bf 100644
--- a/src/server.c
+++ b/src/server.c
@@ -4574,6 +4574,8 @@
 	}
 
 	/* remove srv from addr_node tree */
+	eb32_delete(&srv->conf.id);
+	ebpt_delete(&srv->conf.name);
 	ebpt_delete(&srv->addr_node);
 
 	/* remove srv from idle_node tree for idle conn cleanup */