Fix loop count in universal benchmark script

benchmarks/performance_data/universal/config.jmx.in

 <?xml version="1.0" encoding="UTF-8"?>
-<jmeterTestPlan version="1.2" properties="5.0" jmeter="5.4.1">
+<jmeterTestPlan version="1.2" properties="5.0" jmeter="5.4.3">
   <hashTree>
     <TestPlan guiclass="TestPlanGui" testclass="TestPlan" testname="constant load" enabled="true">
       <stringProp name="TestPlan.comments"></stringProp>
@@ -13,10 +13,10 @@
     </TestPlan>
     <hashTree>
       <ThreadGroup guiclass="ThreadGroupGui" testclass="ThreadGroup" testname="spam group" enabled="true">
-        <stringProp name="ThreadGroup.on_sample_error">continue</stringProp>
+        <stringProp name="ThreadGroup.on_sample_error">stopthread</stringProp>
         <elementProp name="ThreadGroup.main_controller" elementType="LoopController" guiclass="LoopControlPanel" testclass="LoopController" testname="Loop Controller" enabled="true">
           <boolProp name="LoopController.continue_forever">false</boolProp>
-          <intProp name="LoopController.loops">-1</intProp>
+          <stringProp name="LoopController.loops">${LOOP_COUNT}</stringProp>
         </elementProp>
         <stringProp name="ThreadGroup.num_threads">${THREADS}</stringProp>
         <stringProp name="ThreadGroup.ramp_time">0</stringProp>
@@ -172,6 +172,11 @@
             <stringProp name="Argument.value">${__P(call_style, old-style)}</stringProp>
             <stringProp name="Argument.metadata">=</stringProp>
           </elementProp>
+          <elementProp name="LOOP_COUNT" elementType="Argument">
+            <stringProp name="Argument.name">LOOP_COUNT</stringProp>
+            <stringProp name="Argument.value">${__P(call_style, loop_count)}</stringProp>
+            <stringProp name="Argument.metadata">=</stringProp>
+          </elementProp>
         </collectionProp>
       </Arguments>
       <hashTree/>