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

@@ -218,6 +218,8 @@ 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))
     {
+        /* both old and current kv store have to be marked for cleanup */
+        old_metrics->shm_zone->noreuse = 1;
         metrics->shm_zone->noreuse = 1;
     }
 
@@ -230,7 +232,7 @@ ngx_wa_metrics_init(ngx_wa_metrics_t *metrics, ngx_cycle_t *cycle)
 {
     ngx_wasm_shm_kv_t  *old_shm_kv;
 
-    if (metrics->old_metrics && !metrics->shm_zone->noreuse) {
+    if (metrics->old_metrics && !metrics->old_metrics->shm_zone->noreuse) {
         /* reuse old kv store */
         metrics->shm->data = metrics->old_metrics->shm->data;
         return NGX_OK;
@@ -240,14 +242,13 @@ 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;
+    if (metrics->old_metrics && metrics->old_metrics->shm_zone->noreuse) {
+        /* relable current kv store as reusable */
         metrics->shm_zone->noreuse = 0;
 
-        /* realloc old kv store */
         old_shm_kv = ngx_wasm_shm_get_kv(metrics->old_metrics->shm);
 
+        /* realloc old kv store */
         return realloc_metrics(metrics, old_shm_kv->rbtree.root,
                                old_shm_kv->rbtree.sentinel);
     }