Add prescale check to rates combinatorics [standalone code]

This is a small efficiency improvement in the offline computation of the rate overlap between triggers.

It only affects standalone code and is for the benefit of @jmontejo & @aranzazu

Trigger/TrigCost/TrigCostRootAnalysis/Root/MonitorRates.cxx

@@ -680,6 +680,9 @@ namespace TrigCostRootAnalysis {
       if (counterA->getStrDecoration(kDecType) != "Chain") {
         continue; // I'm not a HLT chain counter - next
       }
+      if (isZero(counterA->getDecoration(kDecPrescaleVal) + 1)) {
+        continue; // Prescaled out in rates processing
+      }
 
       if (checkPatternOverlap(counterA->getName(), kFALSE) == kFALSE) continue;
 
@@ -691,6 +694,9 @@ namespace TrigCostRootAnalysis {
         if (counterB->getStrDecoration(kDecType) != "Chain") {
           continue; // I'm not a HLT chain counter - next
         }
+        if (isZero(counterB->getDecoration(kDecPrescaleVal) + 1)) {
+          continue; // Prescaled out in rates processing
+        }
 
         // Same group?
         if (Config::config().getInt(kDoGroupOverlap) == kTRUE