perf test stat: Ignore failures in Default[234] metricgroups

The Default[234] metric groups may contain unsupported legacy
events. Allow those metric groups to fail.

Signed-off-by: Ian Rogers <[e-mail]>
Signed-off-by: Namhyung Kim <[e-mail]>

tools/perf/tests/shell/stat_all_metricgroups.sh

···
       then
         err=2 # Skip
       fi
+    elif [[ "$m" == @(Default2|Default3|Default4) ]]
+    then
+      echo "Ignoring failures in $m that may contain unsupported legacy events"
     else
       echo "Metric group $m failed"
       echo $result