Switch to least saturated dhstore backend as primary write

The current primary is close to full saturation which results in high
origin latency on ingress traffic and consequential high 404 rate.

Switch the primary dhstore to `qiu`, the instance with least disk
saturation.

deploy/manifests/prod/us-east-2/tenant/storetheindex/instances/inga/config.json

@@ -51,12 +51,12 @@
     "ValueStoreDir": "/data/valuestore",
     "ValueStoreType": "none",
     "DHBatchSize": 16384,
-    "DHStoreURL": "http://dhstore.internal.prod.cid.contact",
+    "DHStoreURL": "http://dhstore-qiu:40080",
     "DHStoreClusterURLs": [
       "http://dhstore-tetra:40080",          
       "http://dhstore-seka:40080",
       "http://dhstore-ravi:40080",
-      "http://dhstore-qiu:40080",
+      "http://dhstore.internal.prod.cid.contact",
       "http://dhstore-helga.internal.prod.cid.contact",
       "http://dhstore-porvy.internal.prod.cid.contact"
     ],