Rename imagebackend arguments.

Rename function arguments to something which more clearly indicates
their purpose. No functional changes.

Change-Id: Iedbc5477ac54527b60c520fd7c774e608adb07c0

nova/tests/fake_imagebackend.py

@@ -34,11 +34,11 @@ class Backend(object):
                               size, *args, **kwargs):
                 pass
 
-            def cache(self, fn, fname, size=None, *args, **kwargs):
+            def cache(self, fetch_func, filename, size=None, *args, **kwargs):
                 pass
 
-            def libvirt_info(self, disk_bus, disk_dev,
-                             device_type, cache_mode):
+            def libvirt_info(self, disk_bus, disk_dev, device_type,
+                             cache_mode):
                 info = config.LibvirtConfigGuestDisk()
                 info.source_type = 'file'
                 info.source_device = device_type

nova/tests/test_libvirt.py

@@ -1882,8 +1882,8 @@ class LibvirtConnTestCase(test.TestCase):
             # large disk space.
             self.mox.StubOutWithMock(imagebackend.Image, 'cache')
             imagebackend.Image.cache(context=mox.IgnoreArg(),
-                                     fn=mox.IgnoreArg(),
-                                     fname='otherdisk',
+                                     fetch_func=mox.IgnoreArg(),
+                                     filename='otherdisk',
                                      image_id=123456,
                                      project_id='fake',
                                      size=10737418240L,