Merge of r4833: limit req: fix of rbtree node insertion. Limit req: fix of rbtree node insertion on hash collisions. The rbtree used in ngx_http_limit_req_module has two level of keys, the top is hash, and the next is the value string itself. However, when inserting a new node, only hash has been set, while the value string has been left empty. The bug was introduced in r4419 (1.1.14). Found by Charles Chen.