SeriesServiceImpl.addReleaseYear(): add unit tests

The puzzle `1343-fe3ada44` from #1343 has to be resolved: 

https://github.com/php-coder/mystamps/blob/bc1288a4874f71c66c6b5412c6fc8d1453d4d66d/src/main/java/ru/mystamps/web/feature/series/SeriesServiceImpl.java#L138-L138

The puzzle was created by Slava Semushin on 01-Jun-20.
