[ticket/12855] Dump the container based on DEBUG_CONTAINER instead of DEBUG

PHPBB3-12855
Merge pull request #2737 from Elsensee/ticket/12855

[ticket/12855] Dump the container based on DEBUG_CONTAINER instead of DEBUG

* Elsensee/ticket/12855:
  [ticket/12855] Dump the container based on DEBUG_CONTAINER instead of DEBUG