* fix titan_db_test typo
Signed-off-by: tabokie <xy.tao@outlook.com>

* test purging blob file in fallback mode
Signed-off-by: tabokie <xy.tao@outlook.com>

* fix test
Signed-off-by: tabokie <xy.tao@outlook.com>

* simplify
Signed-off-by: tabokie <xy.tao@outlook.com>