input-selector: Use segment-presence for running_time check
input-selector: Use segment-presence for running_time check

When determining whether the running_time of a pad can be
calculated, check if the segment is in TIME format instead
of using the 'active' field.

Since the latter is set through *any* activity, it's not a
reliable indicator of segment presence.

https://bugzilla.gnome.org/show_bug.cgi?id=739620

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