logging_context_format_string option should be changed in devstack script

[Lan Qi song]

The following error raised when initialize oslo_log module because magnum used the wrong logging_context_format_string option:

Traceback (most recent call last):
  File "/usr/lib/python2.7/logging/__init__.py", line 851, in emit
    msg = self.format(record)
  File "/usr/local/lib/python2.7/dist-packages/oslo_log/handlers.py", line 69, in format
    return logging.StreamHandler.format(self, record)
  File "/usr/lib/python2.7/logging/__init__.py", line 724, in format
    return fmt.format(record)
  File "/usr/local/lib/python2.7/dist-packages/oslo_log/formatters.py", line 235, in format
    return logging.Formatter.format(self, record)
  File "/usr/lib/python2.7/logging/__init__.py", line 467, in format
    s = self._fmt % record.__dict__
KeyError: 'user_name'

We only need to use the default value of logging_context_format_string option

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/186989

[Lan Qi song (lqslan)]

The fix patch: https://review.openstack.org/#/c/186989/

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/186989
Committed: https://git.openstack.org/cgit/openstack/magnum/commit/?id=e666edab5f38278b1c899d4743e9897884002851
Submitter: Jenkins
Branch: master

commit e666edab5f38278b1c899d4743e9897884002851
Author: Lan Qi song <email address hidden>
Date: Sat May 30 16:06:22 2015 +0800

    Change value for logging_context_format_string option

    This patch make logging_context_format_string option to use right
    value in devstack script

    Change-Id: I1e3456014fb22d4ba0ac6cb8de470f1406179f59
    Closes-Bug: #1460269