Exceptions in _heal_instance_info_cache should be shown

[Aaron Rosen]

If an exception occurs in _heal_instance_info_cache the actual stack trace is not shown and is hard to track down something is failing as it's log level is debug.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/60098

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/60098
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=b18b2333a98889f6a4a2fd0e859b466116ce4aac
Submitter: Jenkins
Branch: master

commit b18b2333a98889f6a4a2fd0e859b466116ce4aac
Author: Aaron Rosen <email address hidden>
Date: Wed Dec 4 14:16:05 2013 -0800

    Log exception in _heal_instance_info_cache

    Previously, if errors occurred in _heal_instance_info_cache() they would
    go unnoticed as their log level was debug and the stace trace was not
    displayed. This patch changes that so the exception is logged so periodic
    failures here can be more easily detected and fixed.

    Change-Id: I15bb3e7e29462e930f6159be9f4bbf4980b1270c
    Closes-bug: #1257940