Added a simple check to prevent DoEnduranceUpkeep (1 sec persistent timer)

from constantly checking when client has no endurance drain effects.
This was running 24/7 for all classes.

zone/merc.cpp

@@ -1160,10 +1160,14 @@ void Merc::SetEndurance(int32 newEnd)
 }
 
 void Merc::DoEnduranceUpkeep() {
-	int upkeep_sum = 0;
 
+	if (!HasEndurUpkeep())
+		return;
+
+	int upkeep_sum = 0;
 	int cost_redux = spellbonuses.EnduranceReduction + itembonuses.EnduranceReduction;
 
+	bool has_effect = false;
 	uint32 buffs_i;
 	uint32 buff_count = GetMaxTotalSlots();
 	for (buffs_i = 0; buffs_i < buff_count; buffs_i++) {
@@ -1187,6 +1191,9 @@ void Merc::DoEnduranceUpkeep() {
 
 	if(upkeep_sum != 0)
 		SetEndurance(GetEndurance() - upkeep_sum);
+
+	if (!has_effect)
+		SetEndurUpkeep(false);
 }
 
 void Merc::CalcRestState() {