Azure snapshots can not be restored anymore

While working on elastic#26751 and doing some manual integration testing I found that this elastic#22858 removed an important line of our code:

`AzureRepository` overrides default `initializeSnapshot` method which creates metadata files and do other stuff.

But with PR elastic#22858, I wrote:

```java
    @OverRide
    public void initializeSnapshot(SnapshotId snapshotId, List<IndexId> indices, MetaData clusterMetadata) {
        if (blobStore.doesContainerExist(blobStore.container()) == false) {
            throw new IllegalArgumentException("The bucket [" + blobStore.container() + "] does not exist. Please create it before " +
                " creating an azure snapshot repository backed by it.");
        }
    }
```

instead of

```java
    @OverRide
    public void initializeSnapshot(SnapshotId snapshotId, List<IndexId> indices, MetaData clusterMetadata) {
        if (blobStore.doesContainerExist(blobStore.container()) == false) {
            throw new IllegalArgumentException("The bucket [" + blobStore.container() + "] does not exist. Please create it before " +
                " creating an azure snapshot repository backed by it.");
        }
        super.initializeSnapshot(snapshotId, indices, clusterMetadata);
    }
```

As we never call `super.initializeSnapshot(...)` files are not created and we can't restore what we saved.

Closes elastic#26777.

Author: dadoonet

plugins/repository-azure/src/main/java/org/elasticsearch/repositories/azure/AzureRepository.java

@@ -157,6 +157,7 @@ public void initializeSnapshot(SnapshotId snapshotId, List<IndexId> indices, Met
             throw new IllegalArgumentException("The bucket [" + blobStore.container() + "] does not exist. Please create it before " +
                 " creating an azure snapshot repository backed by it.");
         }
+        super.initializeSnapshot(snapshotId, indices, clusterMetadata);
     }
 
     @Override