We need to send allowReboot in the migration cookie to ensure the same
behavior of the virDomainSetLifecycleAction() API on the destination.

Consider this scenario:

    1. On the source the domain is started with:
        <on_poweroff>destroy</on_poweroff>
        <on_reboot>restart</on_reboot>
        <on_crash>destroy</on_crash>

    2. User calls an API to set "destroy" for <on_reboot>:
        <on_poweroff>destroy</on_poweroff>
        <on_reboot>destroy</on_reboot>
        <on_crash>destroy</on_crash>

    3. The guest is migrated to a different host

    4a. Without the allowReboot in the migration cookie the QEMU
        process on destination would be started with -no-reboot
        which would prevent using the virDomainSetLifecycleAction() API
        for the rest of the guest lifetime.

    4b. With the allowReboot in the migration cookie the QEMU process
        on destination is started without -no-reboot like it was started
        on the source host and the virDomainSetLifecycleAction() API
        continues to work.

The following patch adds a QEMU implementation of the
virDomainSetLifecycleAction() API and that implementation disallows
using the API if all actions are set to "destroy" because we add
"-no-reboot" on the QEMU command line.  Changing the lifecycle action
is in this case pointless because the QEMU process is always terminated.
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>
Signed-off-by: NPavel Hrdina <phrdina@redhat.com>