Spell: Add check for single target to resist/miss channeled spell cancel

Closes  #645

I altered your PR a bit because:

Line with SPELL_MISS_IMMUNE2 should never be hit except for single target target. When spell is AOE, we do not supply unit target so check is redundant.
In second case, SPELL_MISS_RESIST - we want to just check if its the single target target. Like before, AOE does not supply that to the spell so its quicker.
The code is there for a spell like Mind Flay and nothing else really.

src/game/Spells/Spell.cpp

@@ -4267,7 +4267,7 @@ void Spell::WriteSpellGoTargets(WorldPacket& data)
         }
         else
         {
-            if (IsChanneledSpell(m_spellInfo) && (ihit.missCondition == SPELL_MISS_RESIST || ihit.missCondition == SPELL_MISS_REFLECT))
+            if (IsChanneledSpell(m_spellInfo) && (ihit.missCondition == SPELL_MISS_RESIST || ihit.missCondition == SPELL_MISS_REFLECT) && ihit.targetGUID == m_targets.getUnitTargetGuid())
             {
                 m_duration = 0;                              // cancel aura to avoid visual effect continue
                 ihit.effectDuration = 0;