Pull Oslo log fix to enable root logger initialization

Previous log module in Oslo doesn't initialize root logger, which results
in lacking of log message for non-openstack library (such as stevedore).
This patch pull latest log module from Oslo, which has recently merged a
change to enable root logger initialization.

Notice that this change also includes one log modules fix in Oslo which
'unignore' log_format setting.  As a result, one may experience log format
change when using devstack.  To get old log format back, simply assign
a NULL string (aka nothing) to 'log_format' configure option in cinder.conf.
For example, just append cinder.conf with one new line 'log_format = '.

Fix bug: # 1131322

Change-Id: I86396f15ca152512ce6d18d6d424a855b27f495e
Merge "Pull Oslo log fix to enable root logger initialization"