Explicitly prepare shard for peer recovery

This commit moves preparing a shard for peer recovery out of the method
that prepares the recovery request as this was an odd place to change
manipulate the state of the shard.

Author: jasontedor

core/src/main/java/org/elasticsearch/indices/recovery/PeerRecoveryTargetService.java

@@ -184,6 +184,9 @@ private void doRecovery(final long recoveryId) {
 
             cancellableThreads = recoveryTarget.cancellableThreads();
             timer = recoveryTarget.state().getTimer();
+
+            logger.trace("{} preparing shard for peer recovery", recoveryTarget.shardId());
+            recoveryTarget.indexShard().prepareForIndexRecovery();
         }
 
         try {
@@ -353,9 +356,6 @@ private Optional<StartRecoveryRequest> getStartRecoveryRequest(final RecoveryTar
                         recoveryTarget.sourceNode());
             }
 
-            logger.trace("{} preparing shard for peer recovery", recoveryTarget.shardId());
-            recoveryTarget.indexShard().prepareForIndexRecovery();
-
             request = new StartRecoveryRequest(
                 recoveryTarget.shardId(),
                 recoveryTarget.sourceNode(),