Spell Dark Martyrdom and immunities

[sirikfoll]

Description:

While casting dark martydom, the npcs need to be immune to effects that could interrupt the spell cast.
The npcs are not supposed to have knockback/stun/etc immunity at all times, only when casting the spell. This can be seen in retail.
The spell has no InterruptFlags, AuraIF or ChannelIF, and only the Attribute SPELL_ATTR1_DONT_DISPLAY_IN_AURA_BAR
Also client correctly show the "shield" around the cast bar for this spell
Spell Ids: 70903, 70903, 72498, 72499, 72500, 71236, 72495, 72496, 72497

Current behaviour:
Spell can be stoped.

Expected behaviour:
While casting dark martydom, the npcs need to be immune to effects that could interrupt the spell cast.

Steps to reproduce the problem:

1. .npc add 37890
2. .cast self 71236 on the npc
3. .cast 10308 tri on the npc

Branch(es): 3.3.5

TC rev. hash/commit: 3a83dc6