tmf: Handle multiple jobs when updating statistics

When one job is already scheduled, the previous logic did not create
another job preventing subsequent selection from updating the UI in the
statistics view. This commit always computes a new job and cancels the
previous one if present.

[Fixed] Updating statistics now handles concurrent jobs correctly

Signed-off-by: Arnaud Fiorini <fiorini.arnaud@gmail.com>

tmf/org.eclipse.tracecompass.tmf.ui/src/org/eclipse/tracecompass/internal/tmf/ui/viewers/statistics/TmfStatisticsViewer.java

@@ -728,8 +728,10 @@ private void buildStatisticsTree(final ITmfTrace trace, final TmfTimeRange timeR
                 /* No statistics module available for this trace */
                 continue;
             }
-
-            updateJobs.computeIfAbsent(aTrace, k -> {
+            updateJobs.compute(aTrace, (k, v) -> {
+                if (v != null) {
+                    v.cancel(); /* Cancel previous job */
+                }
                 Job job = new StatisticsUpdateJob("Statistics update", aTrace, isGlobal, timeRange, statsMod, this); //$NON-NLS-1$
                 job.setSystem(true);
                 job.schedule();