Snapshot with localdisk not supported

[Eric Fried]

Attempting snapshot with the localdisk driver yields an ugly REST error like:

2017-01-31 13:28:01.043 3394 WARNING nova_powervm.virt.powervm.disk.driver [req-f1b1dd48-5da1-4637-8289-4534149f084b 824c6d7cbe914a02aae461416bac3856 bca011d0d26b40ab9b55c4609038e460 - - -] Failed to map boot disk b_instance_249b of instance instance-00000024 to the management partition from Virtual I/O Server SRVAVIO401: HTTP error 500 for method POST on path /rest/api/uom/VirtualIOServer/21C966C6-9F41-4AE0-A41F-EC422975C0F7?group=ViosSCSIMapping: Internal Server Error -- Logical Volumes can not be associated with more than one
virtual SCSI adapter

We should raise a prettier "not supported" exception instead.

[Eric Fried (efried)]

https://review.openstack.org/#/c/466425/

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/466425
Committed: https://git.openstack.org/cgit/openstack/nova-powervm/commit/?id=58d63fb15d5ae59a4a6071523a9140fe65876cc8
Submitter: Jenkins
Branch: master

commit 58d63fb15d5ae59a4a6071523a9140fe65876cc8
Author: Eric Fried <email address hidden>
Date: Fri May 19 17:28:45 2017 -0500

    Add snapshot capability in DiskAdapter

    Add a 'snapshot' capability in the DiskAdapter superclass, and check it
    from the virt driver's snapshot method. This allows us to generate a
    prettier error when snapshot is attempted with a disk driver that
    doesn't support it.

    The snapshot capability is True for the SSP driver.

    The snapshot capability is True for the localdisk driver if the
    management partition is acting as the VIOS; but False for traditional
    VIOS.

    Change-Id: Ide8c495a4293050f9844e16132b7b751ec50cbf1
    Closes-Bug: #1661395