Hitbox issue inside Towny claims

Summary

When using a custom model with oriented bounding boxes as sub-hitboxes, these can't be hit when spawning a custom mob inside of Towny town claims that have mob spawning turned off. We figured out that MythicMobs uses Slimes to simulate the hitboxes, which apparently can't spawn with the corresponding Towny setting toggled on, even though the settings explicitly allow hostile entities with spawn reason CUSTOM to appear.

This might also be related to the recently fixed bug where MM mobs generally spawned with reason PATROL instead of CUSTOM.

Steps to reproduce

Spawn a custom mob that uses oriented bounding boxes in a Towny town that has mob spawning toggled off.

Current behavior

The sub-hitboxes don't work because the Slimes don't spawn.

Intended correct behavior

The sub-hitboxes should work because the Slimes should be allowed to spawn alongside their parent.

Proposed fixes

• Check the Bukkit SpawnReason for the hidden Slime entities and set it to CUSTOM to allow bypassig the Towny mob settings