A fork's copies start on another server when the source's is full

A fork used to start its copies only on its source's server, and answered no_capacity when that server had no room, even after pausing the source and taking its snapshot. Now its snapshot is copied to a server with room and the copies start there, as a create from a kept snapshot already did. And a time limit (timeoutSeconds) set on a sandbox that is still starting or waking is taken at once, rather than answered busy.