test: Switch to Python3

Python2 will be maintained till end of 2019.  Switch to Python3 by
replacing iteritems() with items() to fix error when runnig test-nap:

	AttributeError: 'dbus.Dictionary' object has no attribute 'iteritems'
diff --git a/test/bluezutils.py b/test/bluezutils.py
index de08cbd..cd89640 100644
--- a/test/bluezutils.py
+++ b/test/bluezutils.py
@@ -15,7 +15,7 @@
 
 def find_adapter_in_objects(objects, pattern=None):
 	bus = dbus.SystemBus()
-	for path, ifaces in objects.iteritems():
+	for path, ifaces in objects.items():
 		adapter = ifaces.get(ADAPTER_INTERFACE)
 		if adapter is None:
 			continue
@@ -35,7 +35,7 @@
 	if adapter_pattern:
 		adapter = find_adapter_in_objects(objects, adapter_pattern)
 		path_prefix = adapter.object_path
-	for path, ifaces in objects.iteritems():
+	for path, ifaces in objects.items():
 		device = ifaces.get(DEVICE_INTERFACE)
 		if device is None:
 			continue