HBASE-20668 Avoid permission change if ExportSnapshot's copy fails

hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/snapshot/ExportSnapshot.java

@@ -1027,15 +1027,18 @@ public class ExportSnapshot extends AbstractHBaseTool implements Tool {
     // The snapshot references must be copied before the hfiles otherwise the cleaner
     // will remove them because they are unreferenced.
     List<Path> travesedPaths = new ArrayList<>();
+    boolean copySucceeded = false;
     try {
-      LOG.info("Copy Snapshot Manifest");
+      LOG.info("Copy Snapshot Manifest from " + snapshotDir + " to " + initialOutputSnapshotDir);
       travesedPaths =
           FSUtils.copyFilesParallel(inputFs, snapshotDir, outputFs, initialOutputSnapshotDir, conf,
               conf.getInt(CONF_COPY_MANIFEST_THREADS, DEFAULT_COPY_MANIFEST_THREADS));
+      copySucceeded = true;
     } catch (IOException e) {
       throw new ExportSnapshotException("Failed to copy the snapshot directory: from=" +
         snapshotDir + " to=" + initialOutputSnapshotDir, e);
     } finally {
+      if (copySucceeded) {
         if (filesUser != null || filesGroup != null) {
           LOG.warn((filesUser == null ? "" : "Change the owner of " + needSetOwnerDir + " to "
               + filesUser)
@@ -1048,6 +1051,7 @@ public class ExportSnapshot extends AbstractHBaseTool implements Tool {
           setPermissionParallel(outputFs, (short)filesMode, travesedPaths, conf);
         }
       }
+    }
 
     // Write a new .snapshotinfo if the target name is different from the source name
     if (!targetName.equals(snapshotName)) {