HDFS-14989. Add a 'swapBlockList' operation to Namenode. (#1819)

* HDFS-14989. Add a 'swapBlockList' operation to Namenode.

* HDFS-14989. Add a 'swapBlockList' operation to Namenode. (Fix checkstyle issues)

* HDFS-14989. Address review comments.

* HDFS-14989. Swap storage policy ID, check destination file genStamp.

* HDFS-14989. Remove unused import.

* HDFS-14989. Address review comment.

* HDFS-14989. Use FSDirectory.resolveLastINode.
5 files changed