[3.3.5] Pets are causing issues with enemy frames in arena

Description:

Hunter/DK's pets are causing the arena frames for their partners to break. This has been reported a long time ago, and its still present, as a gamebreaking bug for arenas.

Expected behaviour:

The arena enemy frames should be updated for the first time when the arena gates open, and not before that.

Steps to reproduce the problem:

Create a hunter, and tame random creature as pet, create 3 more players and invite them in 2 separate groups in order to be able to queue for 2v2 skirmish (or rated, whatever). Queue for 2v2 skirmish, and after the queue pop up, from the hunter's party, enter the game with the hunter's partner first.Then enter the game with the hunter (keep in mind the pet must be summoned and alive, not sure if it is dead or smth else like this). You will see the arena frames of the hunter's partner are showing the hunter's pet, and UNKNOWN owner of him as target, which later on is causing the arena frames to completely mess up addons like gladius etc, makind the whole game ruined for this player, as it is not able to properly target/set focus on the opponents as the gladius is showing only one of the 2 opponents, and the blizzard enemy frames are showing 3 enemies in 2v2 game (or 4 enemies in 3v3 game).

This is a very critical bug, present from 2012 (and maybe before that also)

Branch(es):

3.3.5

TC rev. hash/commit: ce91616

Operating system: Windows 10 x64

Start by tracing the arena enemy-frame update flow for 3.3.5, focusing on how a summoned and alive Hunter or DK pet is represented when partners enter before the owner. Reproduce the 2v2 sequence described and verify that frames first update when the arena gates open, without an extra pet or UNKNOWN owner entry.