Core/Combat: Creature on transport

[Killyana]

Description:
Creatures on transport have a weird behavior, they appear to be in combat but they aren't, event if the client shows some information related to combat.

Steps to reproduce the problem:

1. aggro this https://www.wowhead.com/npc=25026/mutinous-sea-dog
2. Move to the stairs
3. Notice this:
   

Branch(es): 3.3.5

TC rev. hash/commit: rev. 8711c53

[Shauren]

I've seen this happen outside transports (training dummies do that)