Remove bad log message in get_remote_image_service

There was a LOG.debug() message in the
nova.image.glance.get_remote_image_service() call that was incorrect and
misleading:

LOG.debug(_("fetching image %s from glance") % image_href)

This function actually does not fetch any image from Glance -- rather,
it is just used to get the default image service object or an image
service object for use with a remote Glance server.

Change-Id: I2b71c2c52d6593ad4677767a6f2bb40c399fe9eb
Closes-bug: #1292984
Merge "Remove bad log message in get_remote_image_service"