Also include InnoDB undo tablespaces in rsync sst

If --innodb-undo-tablespaces is used, then InnoDB stores undo in a
separate file(s) which whould also be replicated.

This fixes
Issue#337 This filter will cause sst failed at applying undo...
https://github.com/codership/mysql-wsrep/issues/337

scripts/wsrep_sst_rsync.sh

@@ -126,6 +126,7 @@ FILTER=(-f '- /lost+found'
         -f '+ /wsrep_sst_binlog.tar'
         -f '+ /ib_lru_dump'
         -f '+ /ibdata*'
+        -f '+ /undo*'
         -f '+ /*/'
         -f '- /*')