Break config_default into master_site_configs.

masters/master.client.skia/master.cfg

Index: masters/master.client.skia/master.cfg
diff --git a/masters/master.client.skia/master.cfg b/masters/master.client.skia/master.cfg
index 66434b650b571635c1fee13aa1a31bb4e3d60f12..01cd6e2112adb83ed1de9f369e6c44ccfb891e5e 100644
--- a/masters/master.client.skia/master.cfg
+++ b/masters/master.client.skia/master.cfg
@@ -14,12 +14,13 @@ from master import slaves_list
 # This module comes from $(TOPLEVEL_DIR)/site_config ,
 # which must be in the PYTHONPATH.
 import config
+import master_site_config
 
 # These modules come from the local directory.
 import master_builders_cfg
 import master_source_cfg
 
-ActiveMaster = config.Master.Skia
+ActiveMaster = master_site_config.Skia
 
 c = BuildmasterConfig = {}
 c['change_source'] = []