Define bus used by mapper in settings_manager.py

Undefined bus in mapper = obmc.mapper.Mapper(bus) in
settings_manager.py causes a failure. This patch defines
the bus.

Resolves openbmc/openbmc#806

Change-Id: I1989c1246c34f8be98591f439bfa1847f3325e00
Signed-off-by: Sergey Solomin <sergey.solomin@us.ibm.com>
diff --git a/settings_manager.py b/settings_manager.py
index 77e200b..458af5e 100644
--- a/settings_manager.py
+++ b/settings_manager.py
@@ -41,6 +41,7 @@
     Parse dictionary file and return all objects and settings
     in the following format: {obj_name {settings}}
     """
+    bus = get_dbus()
     mapper = obmc.mapper.Mapper(bus)
     allobjects = {}
     queries = {}