Core/Auras: Check min power instead of 0 for SPELL_AURA_OBS_MOD_POWER

Port From (https://github.com/TrinityCore/TrinityCore/commit/c850e2f7801fecd9a56d88dda1fc60e27fd30bdf)

Source/Game/Entities/StatSystem.cs

@@ -177,7 +177,7 @@ namespace Game.Entities
             }
         }
 
-        int GetMinPower(PowerType power) { return power == PowerType.LunarPower ? -100 : 0; }
+        public int GetMinPower(PowerType power) { return power == PowerType.LunarPower ? -100 : 0; }
 
         // returns negative amount on power reduction
         public int ModifyPower(PowerType power, int dVal, bool withPowerUpdate = true)

Source/Game/Spells/Auras/AuraEffect.cs

@@ -5578,8 +5578,13 @@ namespace Game.Spells
             // don't regen when permanent aura and limit is already reached
             if (GetBase().IsPermanent())
             {
-                if ((target.GetPower(powerType) == target.GetMaxPower(powerType) && GetAmount() > 0)
-                    || (target.GetPower(powerType) == 0 && GetAmount() < 0))
+                if (GetAmount() >= 0)
+                {
+                    if (target.GetPower(powerType) >= target.GetMaxPower(powerType))
+                        return;
+                }
+                else
+                    if (target.GetPower(powerType) <= target.GetMinPower(powerType))
                     return;
             }