wait for all backups to complete before producing output

rdiff-manager.py

@@ -81,7 +81,10 @@ if __name__ == '__main__':
         concurrent_num = len(hosts)
     pool = Pool(concurrent_num)
 
+    # Start the work and wait for it to finish
     results = [ (host, pool.apply_async(rdiff_backup, (host, )) ) for host in hosts ]
+    pool.close()
+    pool.join()
 
     for host, r in results:
         print("Backup results for", host['hostname'])