Comment 6 for bug 1562713

Reviewed: https://review.openstack.org/368946
Committed: https://git.openstack.org/cgit/openstack/rally/commit/?id=2bfe9a9928be93cc029241dbaa8c5ac8b0ab33c6
Submitter: Jenkins
Branch: master

commit 2bfe9a9928be93cc029241dbaa8c5ac8b0ab33c6
Author: Andrey Kurilin <email address hidden>
Date: Mon Sep 12 19:01:28 2016 +0300

    [task] Fix verification log

    While fix for bug #1562713 changed the way how to save verification log in
    case of some issues at CLI layer, it did not fixed old saved logs. Also, it
    produced one more bug - IOError trace was saved as list instead of string.

    This patch fixes the way of storage IOError and add migration to fix old data

    Also, we change format of verification_log to dict here
    Change-Id: Iffcf066e7033acd48f1446baebe0b2e9a334449f
    Related-Bug: #1562713