No need to deactivate perf sample colletion

When collecting events with gconly, gccollectonly and gcwithheap flags,
there is no need to disable the perf cpu samples collection.
If you don't want to get the cpu sample, use -noperf on the command-line

Author: Gregory LEOCADIE

src/perfcollect/perfcollect

@@ -1438,21 +1438,18 @@ SetupLTTngSession()
         RunSilent "$lttngcmd enable-event --userspace --tracepoint DotNETRuntime:EventSource"
     elif [ "$gcCollectOnly" == "1" ]
     then
-        usePerf=0
         EnableLTTngEvents ${DotNETRuntime_GCKeyword_GCCollectOnly[@]}
         EnableLTTngEvents ${DotNETRuntimePrivate_GCPrivateKeyword_GCCollectOnly[@]}
         EnableLTTngEvents ${DotNETRuntime_ExceptionKeyword[@]}
     elif [ "$gcOnly" == "1" ]
     then
-        usePerf=0
         EnableLTTngEvents ${DotNETRuntime_GCKeyword[@]}
         EnableLTTngEvents ${DotNETRuntimePrivate_GCPrivateKeyword[@]}
         EnableLTTngEvents ${DotNETRuntime_JitKeyword[@]}
         EnableLTTngEvents ${DotNETRuntime_LoaderKeyword[@]}
         EnableLTTngEvents ${DotNETRuntime_ExceptionKeyword[@]}
     elif [ "$gcWithHeap" == "1" ]
     then
-        usePerf=0
         EnableLTTngEvents ${DotNETRuntime_GCKeyword[@]}
         EnableLTTngEvents ${DotNETRuntime_GCHeapSurvivalAndMovementKeyword[@]}
     else