Add context information to download plugins

This patch sends the context information into the download plugins
via  kwargs.  This will allow download modules like swift to use
the keystone auth information.

Change-Id: I105cc7d7dd76e4eadfeefdc7ca65f9eab38098b7
blueprint: image-multiple-location

nova/image/download/base.py

@@ -20,6 +20,6 @@ from nova import exception
 
 class TransferBase(object):
 
-    def download(self, url_parts, dst_path, metadata, **kwargs):
+    def download(self, context, url_parts, dst_path, metadata, **kwargs):
         raise exception.ImageDownloadModuleNotImplementedError(
             method_name='download')

nova/image/download/file.py

@@ -141,7 +141,7 @@ class FileTransfer(xfer_base.TransferBase):
         new_path = path.replace(glance_mount, nova_mount, 1)
         return new_path
 
-    def download(self, url_parts, dst_file, metadata, **kwargs):
+    def download(self, context, url_parts, dst_file, metadata, **kwargs):
         self.filesystems = self._get_options()
         if not self.filesystems:
             #NOTE(jbresnah) when nothing is configured assume legacy behavior

nova/image/glance.py

@@ -326,7 +326,7 @@ class GlanceImageService(object):
                 xfer_mod = self._get_transfer_module(o.scheme)
                 if xfer_mod:
                     try:
-                        xfer_mod.download(o, dst_path, loc_meta)
+                        xfer_mod.download(context, o, dst_path, loc_meta)
                         msg = _("Successfully transferred "
                                 "using %s") % o.scheme
                         LOG.info(msg)