update script according to empty sink issue #2

fvt_scripts/change_stream_rule.jmx

@@ -599,7 +599,7 @@
         <stringProp name="ThreadGroup.on_sample_error">continue</stringProp>
         <elementProp name="ThreadGroup.main_controller" elementType="LoopController" guiclass="LoopControlPanel" testclass="LoopController" testname="Loop Controller" enabled="true">
           <boolProp name="LoopController.continue_forever">false</boolProp>
-          <stringProp name="LoopController.loops">3</stringProp>
+          <stringProp name="LoopController.loops">1</stringProp>
         </elementProp>
         <stringProp name="ThreadGroup.num_threads">1</stringProp>
         <stringProp name="ThreadGroup.ramp_time">1</stringProp>