typefind: Reset segment when deactivating pull mode or not running in pull mode
typefind: Reset segment when deactivating pull mode or not running in pull mode

We use the segment format to detect if we run the streaming thread or not.
Without resetting we might believe we do so, although we only did in the past
and are now running in e.g. push mode.

https://bugzilla.gnome.org/show_bug.cgi?id=745073

StreamUtils/gstreamer,shelsonjava/gstreamer,centricular/gstreamer,StreamUtils/gstreamer,krichter722/gstreamer,centricular/gstreamer,mparis/gstreamer,shelsonjava/gstreamer,shelsonjava/gstreamer,StreamUtils/gstreamer,jpxiong/gstreamer,shelsonjava/gstreamer,StreamUtils/gstreamer,krichter722/gstreamer,jpxiong/gstreamer,jpxiong/gstreamer,mparis/gstreamer,jpxiong/gstreamer,StreamUtils/gstreamer,krichter722/gstreamer,krichter722/gstreamer,mparis/gstreamer,shelsonjava/gstreamer,centricular/gstreamer,mparis/gstreamer,jpxiong/gstreamer,krichter722/gstreamer,centricular/gstreamer,mparis/gstreamer,centricular/gstreamer