HBASE-23920 Pass --copy-to argument in ExportSnapshot tests (#1234)

Signed-off-by: Jan Hentschel <janh@apache.org>

hbase-mapreduce/src/test/java/org/apache/hadoop/hbase/snapshot/TestExportSnapshot.java

@@ -213,6 +213,7 @@ public class TestExportSnapshot {
     opts.add("--snapshot");
     opts.add(snapshotName);
     opts.add("--copy-to");
+    opts.add(tgtDir.toString());
     if (!targetName.equals(snapshotName)) {
       opts.add("--target");
       opts.add(targetName);