Uncore events as group leaders fail in per-thread mode causing exit
errors. Enable system-wide for metricgroup testing. This fixes the HPC
metric group when tested on skylakex.

Fixes: 4a87dea9 ("perf test: Workload test of metric and metricgroups")
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/r/20211223183948.3423989-1-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>