detach boot device volume without warning

[lirenke]

If I use block_device_mapping_v2 api to set a backend volume as boot device for instance. The instance will be launched by this remote volume successfully.
But, in such case, we can also use detach api to force this boot device being detached. So, when we do it, the guestOS of this instance would be damaged, and the whole system would not work normally if do a I/O operation. It seems can not resume.
I think we should give a warning for user at least or even forbiden this operation.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/75552

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/75552
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=7fbb42296970ee30d21bbd66b144a2ab421aa17f
Submitter: Jenkins
Branch: master

commit 7fbb42296970ee30d21bbd66b144a2ab421aa17f
Author: Yunhong Jiang <email address hidden>
Date: Fri Feb 21 18:11:03 2014 -0800

    Don't detach root device volume

    Detach a root device volume may cause various guest error. Although
    we can argue that it's user response to not detach the root device
    volume, a check in nova will be more helpful.

    We can either give a warning message, or not allow it. This patch
    forbids this operation, considering that even in real system, remove
    root device does not make much sense.

    Closes-Bug: #1279300

    DocImpact

    Change-Id: I01f086be668b35442a2f139f4d7dc96884a3bda6
    Signed-off-by: Yunhong Jiang <email address hidden>

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/havana
Review: https://review.openstack.org/82695

[OpenStack Infra (hudson-openstack)]

Change abandoned by Alan Pevec (<email address hidden>) on branch: stable/havana
Review: https://review.openstack.org/82695
Reason: Final Havana release 2013.2.4 has been cut and stable/havana is going to be removed in a week.