perf tests stat+std_output: Fix shellcheck warnings about word...

perf tests stat+std_output: Fix shellcheck warnings about word splitting/quoting and local variables

Running shellcheck on stat_std_output testcase throws
below warning:

   In tests/shell/stat+std_output.sh line 9:
   . $(dirname $0)/lib/stat_output.sh
     ^-----------^ SC2046 (warning): Quote this to prevent word splitting.

   In tests/shell/stat+std_output.sh line 32:
   	   local -i cnt=0
                    ^-^ SC2034 (warning): cnt appears unused. Verify use (or export if used externally).

Fixed the warning by adding quotes to avoid word splitting
and removed unused variable "cnt" at line 32.
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/20230709182800.53002-27-atrajeev@linux.vnet.ibm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/shell/stat+std_output.sh

@@ -6,7 +6,7 @@
 
 set -e
 
-. $(dirname $0)/lib/stat_output.sh
+. "$(dirname $0)"/lib/stat_output.sh
 
 stat_output=$(mktemp /tmp/__perf_test.stat_output.std.XXXXX)
 
@@ -28,7 +28,6 @@ trap trap_cleanup EXIT TERM INT
 
 function commachecker()
 {
-	local -i cnt=0
 	local prefix=1
 
 	case "$1"