Merge of r4422: Fixed error handling in ngx_event_connect_peer(). Previously if ngx_add_event() failed a connection was freed two times (once in the ngx_event_connect_peer(), and again by a caller) as pc->connection was left set. Fix is to always use ngx_close_connection() to close connection properly and set pc->connection to NULL on errors. Patch by Piotr Sikora.