youtube: Add initalise microseconds published value to 0
youtube: Add initalise microseconds published value to 0

This should mean that the GTimeValue can be correctly parsed to iso8601
using g_time_val_to_iso8601

Fixes https://bugzilla.gnome.org/show_bug.cgi?id=643924

jasuarez/grilo-plugins,vrutkovs/grilo-plugins,kyoushuu/grilo-plugins,GNOME/grilo-plugins,MikePetullo/grilo-plugins,grilofw/grilo-plugins,kyoushuu/grilo-plugins,jasuarez/grilo-plugins,vrutkovs/grilo-plugins,MikePetullo/grilo-plugins,MikePetullo/grilo-plugins,MathieuDuponchelle/grilo-plugins,GNOME/grilo-plugins,kyoushuu/grilo-plugins,vrutkovs/grilo-plugins,MathieuDuponchelle/grilo-plugins,MathieuDuponchelle/grilo-plugins,MathieuDuponchelle/grilo-plugins,grilofw/grilo-plugins,vrutkovs/grilo-plugins