Fix for HER-1942 CheckpointService: inconsistent synchronization around use of isRunning. Doubtful if isRunning thing is a real problem, but it looks like a good idea to synchronize this method anyway, in case there are concurrent calls to it.

* CheckpointService.java
    setRecoveryCheckpointByName() - mark synchronized

engine/src/main/java/org/archive/crawler/framework/CheckpointService.java

@@ -325,7 +325,7 @@ public class CheckpointService implements Lifecycle, ApplicationContextAware, Ha
      * 
      * @param selectedCheckpoint
      */
-    public void setRecoveryCheckpointByName(String selectedCheckpoint) {
+    public synchronized void setRecoveryCheckpointByName(String selectedCheckpoint) {
         if(isRunning) {
             throw new RuntimeException("may not set recovery Checkpoint after launch");
         }