[CB] Remove references to chunklist. Fixes BUKKIT-5190

##### The Issue:
Commit c576054539790bdeb35285f62863d74b48c0782d removed the `chunklist` collection stored in ChunkProviderServer, however it has been partially restored in some places by 7e1ac0a77129b169704c1e222ff2deb3ab6cd2d2.  As not all references to this were restored, this has caused the `chunklist` and `chunks` collections to become out of sync, resulting in a memory leak

##### Justification for this PR:
This commit removes `chunklist` from `ChunkProviderServer` again.  As no chunks are ever retrieved from this list (only added and deleted, by some but not all methods) this has no side effects.

##### JIRA Ticket: 
BUKKIT-5190 - https://bukkit.atlassian.net/browse/BUKKIT-5190