Make v2 image tags test not load system policy

Since commit 74a8601, I'm seeing this test attempting to load
/etc/glance/policy.conf.

Switch to using IsolatedUnitTest which copies the policy into a
temp dir.

Change-Id: Ibd84ed753de5abf91ee597918ba56130ddd0550e
Sync latest cfg and log from oslo-incubator

Changes include:

  c5984ba Move logging config options into the log module
  751c35b Verbose should not enable debug level logging
  edcdd25 Improve millisecond logging
  a8973c5 Revert "Support lookup of value using "group.key""

The most significant of these changes is defaulting to the WARNING log
level which was discussed on openstack-dev:

  http://lists.openstack.org/pipermail/openstack-dev/2013-January/004223.html

This is behaviour already documented in doc/source/configuring.rst at
least.

Fixes bug #989269

DocImpact

Change-Id: I8ed9107193a811f50ecfd9b34e99e933774405ab
Update glance config files with log defaults

The default for the verbose config option is False and the sample config
file should reflect that.

Also, comment out the defaults of the config options so that it is clear
that the sample file is showing the default in the code rather than
overriding it.

Change-Id: I3913ea54465658d93dc56e014dfe5d911b0541d6
Log exception details.

When there is an error while initializing the backing store,
log entrires are now displaying more details specifying
the reason of failure.

Also instead of normal info message, log entries display
warnings in this case.

Fixes: bug #1103073
Change-Id: Icb7cc3c27325cfb0e4d62f466d28ecf9995d91ac
Updated image loop to not use an enumerator

*  We are not using the enumerator in the loop. So this has been rewritten to not use it.

Change-Id: I18cab2556190e8ce5c202c5f5e7b8e6b3dfe8f59
Merge "Sync latest cfg and log from oslo-incubator"
Merge "Log exception details."
Merge "Update glance config files with log defaults"
Merge "Make v2 image tags test not load system policy"