The first operation returns a token, which can be passed to the second
one to actually perform clone operation. This way the caller needs have
power over both source and destination VMs (or at least appropriate
volumes), so it's easier to enforce appropriate qrexec policy.
The pending tokens are stored on Qubes() instance (as QubesAdminAPI is
not persistent). It is design choice to keep them in RAM only - those
are one time use and this way restarting qubesd is a simple way to
invalidate all of them. Otherwise we'd need some additional calls like
CloneCancel or such.
QubesOS/qubes-issues#2622