Core/Spells: fix cast time talent bonus of channeled spells

This fixes the cast time talent bonus of channeled spells, including Improved Succubus (https://github.com/TrinityCore/TrinityCore/issues/1543)
that can apply spellmods twice

what about changing the order of the conditions in Unit::ModSpellCastTime? 
```c++
...
    // called from caster
    if (Player* modOwner = GetSpellModOwner())
        modOwner->ApplySpellMod(spellInfo->Id, SPELLMOD_CASTING_TIME, castTime, spell);

    if (spellInfo->IsChanneled() && !(spellInfo->AttributesEx5 & SPELL_ATTR5_HASTE_AFFECT_DURATION))
        return;
...
```