[nrktv:series] Fix extraction
diff --git a/youtube_dl/extractor/nrk.py b/youtube_dl/extractor/nrk.py
index 5f43e692f43..60933f069c4 100644
--- a/youtube_dl/extractor/nrk.py
+++ b/youtube_dl/extractor/nrk.py
@@ -406,7 +406,7 @@ class NRKTVSerieBaseIE(InfoExtractor):
     def _extract_series(self, webpage, display_id, fatal=True):
         config = self._parse_json(
             self._search_regex(
-                (r'INITIAL_DATA_*\s*=\s*({.+?})\s*;',
+                (r'INITIAL_DATA(?:_V\d)?_*\s*=\s*({.+?})\s*;',
                  r'({.+?})\s*,\s*"[^"]+"\s*\)\s*</script>'),
                 webpage, 'config', default='{}' if not fatal else NO_DEFAULT),
             display_id, fatal=False)

## Please follow the guide below

- You will be asked some questions, please read them **carefully** and answer honestly
- Put an `x` into all the boxes [ ] relevant to your *pull request* (like that [x])
- Use *Preview* tab to see how your *pull request* will actually look like

---

### Before submitting a *pull request* make sure you have:
- [x] At least skimmed through [adding new extractor tutorial](https://github.com/ytdl-org/youtube-dl#adding-support-for-a-new-site) and [youtube-dl coding conventions](https://github.com/ytdl-org/youtube-dl#youtube-dl-coding-conventions) sections
- [x] [Searched](https://github.com/ytdl-org/youtube-dl/search?q=is%3Apr&type=Issues) the bugtracker for similar pull requests
- [x] Checked the code with [flake8](https://pypi.python.org/pypi/flake8)

### In order to be accepted and merged into youtube-dl each piece of code must be in public domain or released under [Unlicense](http://unlicense.org/). Check one of the following options:
- [x] I am the original author of this code and I am willing to release it under [Unlicense](http://unlicense.org/)
- [ ] I am not the original author of this code but it is in public domain or released under [Unlicense](http://unlicense.org/) (provide reliable evidence)

### What is the purpose of your *pull request*?
- [x] Bug fix
- [ ] Improvement
- [ ] New extractor
- [ ] New feature

---

### Description of your *pull request* and other information

NRK has made a minor change to their site and downloading series no longer works. This change fixes it and `TestDownload.test_NRKTVSeason` now passes.
