gstpipewiresrc: break out of wait_started() also on STATE_UNCONNECTED

When the session manager sends an error to the client, it typically also destroys the node after the error, which causes the stream to go to STATE_UNCONNECTED via proxy_removed(). In that case, make sure we exit the loop early, otherwise it will take 30 seconds to unblock gst_element_set_state()

This is a revised version of the fix that was commited via !1763 (merged) and then reverted, as it was problematic. Now the code ensures that it breaks out only if the state was previously CONNECTING or higher.