Glance: make logging configurable...

Adds top level glance.debug and glance.verbose config parameters
to control Glance logging.

As part of this change we are also:

 - Dropping --debug from the service config files. This cause the
  previous Glance log configuration to always log at the DEBUG level.

 - Remove the logging.conf file. The previous log file was also set
  to log at a DEBUG level. To get the same effect you can now
  just enable verbose/debug.

 - Drop --log-config from the service config files. We do this because
  we are dropping logging.conf.

 - Remove log_file from glance-api.conf and glance-registry.conf. This
  gives us the same behaviour as before where Glance logged using the
  init system logger.

The motivation for this change is primarily two things:

1) Glance should log at the WARNING level by default in production.
 (Not DEBUG as it did previously)

2) When making use of this element for CI we may want to more easily
 control the log level (and default to DEBUG). Using the new
 glance.debug and glance.verbose element parameters will make this
 easier.

Change-Id: I20e83682af0a46e455ba8f216bbd5e2f1e04ec16
Merge "Glance: make logging configurable..."