migration: Rename normal to normal_pages Rest of counters that refer to pages has a _pages suffix. And historically, this showed the number of full pages transferred. The name "normal" refered to the fact that they were sent without any optimization (compression, xbzrle, zero_page, ...). Signed-off-by: Juan Quintela <quintela@redhat.com> Reviewed-by: Peter Xu <peterx@redhat.com>