Support for lazily instantiated loggers

As part of code review for LP #1161031, there was a suggestion
to lazily instantiate the logger in oslo. The use case was when
creating LOG at a module level when we have not yet called
logging.setup, we needed a way to delay creating actual loggers

Added a handlers property in ContextAdapter so the existing testcase
can be used for lazy loggers as well

Change-Id: Iae2e379f8a0d2d38836645e7648294dee97deaaa
Merge "Support for lazily instantiated loggers"