Merge of r3972, r3973, r3974:

Merge of r3972, r3973, r3974:

Cache fixes:

*) do not close connection if cache file is too small: replace it with
   valid one
*) rename ngx_http_file_cache_manager_sleep() to
   ngx_http_file_cache_loader_sleep() and do not use it all in cache manager:
   this is a vestige of the times when cache manager loaded cache
*) set correct configuration file values while adding path