guardianvideos: fix URL format string
guardianvideos: fix URL format string

The online service complains loudly if passed 1.0 instead of 1,
let's make sure values are formatted as integers.

https://bugzilla.gnome.org/show_bug.cgi?id=748224

GNOME/grilo-plugins,jasuarez/grilo-plugins,GNOME/grilo-plugins,MikePetullo/grilo-plugins,grilofw/grilo-plugins,grilofw/grilo-plugins,jasuarez/grilo-plugins,MikePetullo/grilo-plugins,MikePetullo/grilo-plugins