Fix test

Change-Id: If87353d4cdc540b271c183f339dd704e42cb8b46

Author: jojochuang

hadoop-ozone/ozone-manager/src/test/java/org/apache/hadoop/ozone/om/snapshot/TestSnapshotDiffManagerMXBean.java

@@ -96,7 +96,11 @@ public void setUp(@TempDir Path tempDir) throws IOException, RocksDBException {
     when(ozoneManager.getConfiguration()).thenReturn(conf);
     when(ozoneManager.getMetrics()).thenReturn(mock(OMMetrics.class));
     OMMetadataManager omMetadataManager = mock(OMMetadataManager.class);
-    when(omMetadataManager.getStore()).thenReturn(mock(org.apache.hadoop.hdds.utils.db.RDBStore.class));
+    org.apache.hadoop.hdds.utils.db.RDBStore rdbStore =
+        mock(org.apache.hadoop.hdds.utils.db.RDBStore.class);
+    when(rdbStore.getSnapshotMetadataDir())
+        .thenReturn(tempDir.toAbsolutePath().toString());
+    when(omMetadataManager.getStore()).thenReturn(rdbStore);
     when(ozoneManager.getMetadataManager()).thenReturn(omMetadataManager);
     when(ozoneManager.getOmSnapshotManager()).thenReturn(mock(OmSnapshotManager.class));