ges-launch: Remember URIS that we tried to discover
ges-launch: Remember URIS that we tried to discover

So we do not fail several time trying to discover the same URI

Conflicts:
	tools/ges-launch.c

cfoch/ges,cfoch/gst-editing-services,cfoch/gst-editing-services,cfoch/gst-editing-services,cfoch/ges,cfoch/gst-editing-services,cfoch/ges,cfoch/ges