Import latest log module from oslo

Deprecates log_format in favor of the formatting options used by the
context aware formatter, such as logging_default_format_string.

Changes the default logging formatter back to a colorful and context
aware formatter.  The default was inadvertently changed in the great
oslo sync at the start of Havana, this returns it to what was in at the
end of Grizzly.

Adds support for lazy instantiation of the logger.

Bug 1167081
Bug 1165211

Change-Id: Ibe41afc6e9d7b432453785819821b3c8f0078613
Merge "Import latest log module from oslo"