Fix testSnapshotClosedIndex in 7.3 (#44759)

* We have to wait for the shards before closing. This was fixed in line with some other work in 7.4 but never backported to 7.3
* Closes #44750

Author: original-brownbear

server/src/test/java/org/elasticsearch/snapshots/SharedClusterSnapshotRestoreIT.java

@@ -1569,7 +1569,7 @@ public void testSnapshotClosedIndex() throws Exception {
         createIndex("test-idx", "test-idx-closed");
         ensureGreen();
         logger.info("-->  closing index test-idx-closed");
-        assertAcked(client.admin().indices().prepareClose("test-idx-closed"));
+        assertAcked(client.admin().indices().prepareClose("test-idx-closed").setWaitForActiveShards(ActiveShardCount.ALL));
         ClusterStateResponse stateResponse = client.admin().cluster().prepareState().get();
         assertThat(stateResponse.getState().metaData().index("test-idx-closed").getState(), equalTo(IndexMetaData.State.CLOSE));
         assertThat(stateResponse.getState().routingTable().index("test-idx-closed"), notNullValue());