nvme/perf: Fix destroy of uninitialized barrier

Destroy of uninitialized barrier fails with SIGFPE signal.

Fixes: 1721

Signed-off-by: Evgeniy Kochetov <evgeniik@nvidia.com>
Change-Id: Ic3a18a13059c1b9d706f24c390f070dc7663f6f4
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/5567
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Aleksey Marchuk <alexeymar@mellanox.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>

examples/nvme/perf/perf.c

@@ -2442,8 +2442,9 @@ int main(int argc, char **argv)
 
 	print_stats();
 
-cleanup:
 	pthread_barrier_destroy(&g_worker_sync_barrier);
+
+cleanup:
 	if (thread_id && pthread_cancel(thread_id) == 0) {
 		pthread_join(thread_id, NULL);
 	}