config: version cache: fix ordering of datastore generation increase

Fixes: 118deb4d (pbs-datastore: use ConfigVersionCache for datastore)
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

pbs-config/src/config_version_cache.rs

@@ -157,6 +157,6 @@ impl ConfigVersionCache {
         self.shmem
             .data()
             .datastore_generation
-            .fetch_add(1, Ordering::Acquire)
+            .fetch_add(1, Ordering::AcqRel)
     }
 }