pad: Don't fail latency query on unlinked pads
pad: Don't fail latency query on unlinked pads

A single unlinked pad can make the latency query fail across the
pipeline, which is probably not desirable. Instead, we return a default
anything goes value.

Perhaps we should also be emitting a gst_message_new_latency() when a
PLAYING element has one of its pads linked.

https://bugzilla.gnome.org/show_bug.cgi?id=745197

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