clean up exception handling on evacuate

[Sulochan Acharya]

Need to clean up the catch all exception handling on evacuate extension, and bring it in line
with the v3 extension.

Reference see comments on: https://review.openstack.org/#/c/40192/

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/41131

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/41131
Committed: http://github.com/openstack/nova/commit/41fb99158daee51785e9d026ec9de5123176efe2
Submitter: Jenkins
Branch: master

commit 41fb99158daee51785e9d026ec9de5123176efe2
Author: Sulochan Acharya <email address hidden>
Date: Fri Aug 9 11:06:04 2013 -0500

    Cleanup exception handling on evacuate

    Some cleanup around catchall exception handing
    on evacuate v2 extension to bring it in line
    with v3 exception handling. Tests included.

    Fixes bug 1210570

    Change-Id: I2f2f958acb80240c0fb25f3d538fa204611a33d1