Only go to READY in setup_pipeline, this is enough to get the caps. We
don't want to go to PAUSED yet because we don't want to negotiate a
format.
Mark the source busy after we configured the capsfilter so that we can
let the source negotiate correctly.
Send the base-time to the client so that it can calibrarte the clock.
Wait until we are completely negotiated before completing the state
change to paused. This makes it possible to provide a clock and decide
if we are live or not.
