Add image logging config for nodepool

An upcoming change to nodepool supports logging the output from
the image creation process.  Use it.

Change-Id: I3a45a30f813d0f7b9fff4f602b945d72f2dcda3e

modules/nodepool/files/logging.conf

@@ -1,8 +1,8 @@
 [loggers]
-keys=root,nodepool,requests
+keys=root,nodepool,requests,image
 
 [handlers]
-keys=console,debug,normal
+keys=console,debug,normal,image
 
 [formatters]
 keys=simple
@@ -21,6 +21,12 @@ level=DEBUG
 handlers=debug,normal
 qualname=nodepool
 
+[logger_image]
+level=INFO
+handlers=image
+qualname=nodepool.image.build
+propagate=0
+
 [handler_console]
 level=WARNING
 class=StreamHandler
@@ -39,6 +45,12 @@ class=logging.handlers.TimedRotatingFileHandler
 formatter=simple
 args=('/var/log/nodepool/nodepool.log', 'midnight', 1, 30,)
 
+[handler_image]
+level=INFO
+class=logging.handlers.TimedRotatingFileHandler
+formatter=simple
+args=('/var/log/nodepool/image.log', 'midnight', 1, 30,)
+
 [formatter_simple]
 format=%(asctime)s %(levelname)s %(name)s: %(message)s
 datefmt=