better mehtod name

modules/elasticsearch/src/main/java/org/elasticsearch/cluster/routing/MutableShardRouting.java

@@ -91,7 +91,7 @@ public class MutableShardRouting extends ImmutableShardRouting {
         primary = true;
     }
 
-    public void moveToBackup() {
+    public void moveFromPrimary() {
         if (!primary) {
             throw new IllegalShardRoutingStateException(this, "Already primary, can't move to backup");
         }

modules/elasticsearch/src/main/java/org/elasticsearch/cluster/routing/strategy/ShardsRoutingStrategy.java

@@ -189,7 +189,7 @@ public class ShardsRoutingStrategy extends AbstractComponent {
                             assert !shardEntry2.primary();
 
                             changed = true;
-                            shardEntry.moveToBackup();
+                            shardEntry.moveFromPrimary();
                             shardEntry2.moveToPrimary();
                             elected = true;
                             break;