hotfix(metrics) old metrics cleanup

`ngx_wa_metrics_init_conf` seems a more appropriate place to set
`old_metrics->shm_zone->noreuse` to 1.

Then `ngx_wa_metrics_init` only acts according to the then configured
values.

src/common/metrics/ngx_wa_metrics.c

@@ -218,7 +218,7 @@ ngx_wa_metrics_init_conf(ngx_wa_metrics_t *metrics, ngx_conf_t *cf)
         && (metrics->workers != old_metrics->workers
             || metrics->config.slab_size != old_metrics->config.slab_size))
     {
-        metrics->shm_zone->noreuse = 1;
+        old_metrics->shm_zone->noreuse = 1;
     }
 
     return NGX_CONF_OK;
@@ -240,11 +240,7 @@ ngx_wa_metrics_init(ngx_wa_metrics_t *metrics, ngx_cycle_t *cycle)
         return NGX_ERROR;
     }
 
-    if (metrics->old_metrics && metrics->shm_zone->noreuse) {
-        /* mark the old kv store for cleanup during SIGHUP old_cycle free */
-        metrics->old_metrics->shm_zone->noreuse = 1;
-        metrics->shm_zone->noreuse = 0;
-
+    if (metrics->old_metrics && metrics->old_metrics->shm_zone->noreuse) {
         /* realloc old kv store */
         old_shm_kv = ngx_wasm_shm_get_kv(metrics->old_metrics->shm);