[server] Remove storage partitions not assigned to current host. Drop…

… storage engine if all partitions have been dropped and when idealState is null.

clients/da-vinci-client/src/main/java/com/linkedin/davinci/storage/StorageService.java

@@ -404,7 +404,9 @@ public synchronized void checkWhetherStoragePartitionsShouldBeKeptOrNot(SafeHeli
           removeStorageEngine(storeName);
         }
       } else {
-        removeStorageEngine(storeName);
+        if (storageEngine.getPartitionIds().isEmpty()) {
+          removeStorageEngine(storeName);
+        }
       }
     }
   }