tests/shell: Fix shellcheck issues in tests/shell/stat+shadow_stat.sh tetscase

Running shellcheck on stat+shadow_stat.sh generates below
warning

In tests/shell/stat+csv_summary.sh line 26:
while read _num _event _run _pct
^--^ SC2034: _num appears unused. Verify use (or export if used externally).
^----^ SC2034: _event appears unused. Verify use (or export if used externally).
^--^ SC2034: _run appears unused. Verify use (or export if used externally).
^--^ SC2034: _pct appears unused. Verify use (or export if used externally).

This variable is intentionally unused since it is
needed to parse through the output. commit used "_"
as a prefix for this throw away variable. But this
stil shows warning with shellcheck v0.6. Fix this
by only using "_" instead of prefix and variable name.

Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Tested-by: Ian Rogers <irogers@google.com>
Reviewed-by: Kajol Jain <kjain@linux.ibm.com>
Cc: maddy@linux.ibm.com
Cc: disgoel@linux.vnet.ibm.com
Cc: linuxppc-dev@lists.ozlabs.org
Link: https://lore.kernel.org/r/20230907171540.36736-3-atrajeev@linux.vnet.ibm.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

perf tests stat+csv_summary: Fix unused variable references detected via shellcheck

Running shellcheck on stat+csv_summary.sh throws below warnings:

In tests/shell/stat+csv_summary.sh line 26:
while read num event run pct
^-^ SC2034 (warning): num appears unused. Verify use (or export if used externally).
^---^ SC2034 (warning): event appears unused. Verify use (or export if used externally).
^-^ SC2034 (warning): run appears unused. Verify use (or export if used externally).
^-^ SC2034 (warning): pct appears unused. Verify use (or export if used externally).

These variables are intentionally unused since they are needed to parse
through the output. Use "_" as a prefix for these throw away variables.

Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Disha Goel <disgoel@linux.vnet.ibm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: linuxppc-dev@lists.ozlabs.org
Link: https://lore.kernel.org/r/20230709182800.53002-8-atrajeev@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

perf test: Add CSV summary test

The patch "perf stat: Align CSV output for summary mode" aligned CSV
output and added "summary" to the first column of summary lines.

Now we check if the "summary" string is added to the CSV output.

If we set '--no-csv-summary' option, the "summary" string would not be
added, also check with this case.

Committer testing:

$ perf test csv
84: perf stat csv summary test : Ok
$

Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@redhat.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: Jin Yao <yao.jin@intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20210319070156.20394-2-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>