Add missing runtime to tvmaze collection display

When using tvmaze.py to retrieve Collection information, the
runtime information was not being displayed. This update adds
it to output. For example, the Collection information for
the TV show "Hogan's Heroes" is now:

/usr/share/mythtv/metadata/Television/tvmaze.py -C 1475
<?xml version='1.0' encoding='UTF-8'?>
<metadata>
  <item>
    <title>Hogan's Heroes</title>
...
    <inetref>1475</inetref>
    <imdb>tt0058812</imdb>
    <collectionref>1475</collectionref>
    <language>en</language>
    <releasedate>1965-09-17</releasedate>
    <userrating>8.000000</userrating>
    <popularity>85.0</popularity>
    <year>1965</year>
    <runtime>30</runtime>
...
  </item>
</metadata>

Refs: #654

mythtv/programs/scripts/metadata/Television/tvmaze.py

@@ -536,6 +536,7 @@ def buildCollection(tvinetref, opts):
     m.imdb = check_item(m, ("imdb", str(show_info.external_ids['imdb'])))
     m.language = check_item(m, ("language", str(locales.Language.getstored(show_info.language))))
     m.userrating = check_item(m, ("userrating", show_info.rating['average']))
+    m.runtime = check_item(m, ("runtime", show_info.runtime))
     try:
         m.popularity = check_item(m, ("popularity", float(show_info.weight)), ignore=False)
     except (TypeError, ValueError):