Core: fixed ENOSPC handling for error logs. For each connection a new ngx_log_t structure is created, and saving anything into disk_full_time field in this structure doesn't affect other connections. Fix is to move the disk_full_time field into the ngx_open_file_t structure.

--- a/src/core/ngx_log.h
+++ b/src/core/ngx_log.h
@@ -53,8 +53,6 @@ struct ngx_log_s {
 
     ngx_atomic_uint_t    connection;
 
-    time_t               disk_full_time;
-
     ngx_log_handler_pt   handler;
     void                *data;