migration: go to paused state after finishing incoming migration with -S

migration: go to paused state after finishing incoming migration with -S

At the end of migration the machine has started already, and cannot be
destroyed without losing the guest's data.  Hence, prelaunch is the
wrong state.  Go to the paused state instead.  QEMU would reach that
state anyway (after running the guest for the blink of an eye) if the
"stop" command had been received after the start of migration.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>