Fix check of fetched data

Commit c6634ee0746d8183ff2b13c4ace4261e3c53ede7 introduces check for
fetched data in case they are not local but remote from a repo, and skip
repos to be added to the SWU file. This breaks local install because the
check is not done on an absolute pathname.

Reported-by: Vincent Prince <vincent.prince.fr@gmail.com>
Signed-off-by: Stefano Babic <sbabic@denx.de>
Tested-by: Vincent Prince <vincent.prince.fr@gmail.com>

classes/swupdate.bbclass

@@ -98,7 +98,7 @@ python do_swuimage () {
     for url in fetch.urls:
         local = fetch.localpath(url)
         filename = os.path.basename(local)
-        if (filename != 'sw-description') and (os.path.isfile(filename)):
+        if (filename != 'sw-description') and (os.path.isfile(local)):
             shutil.copyfile(local, os.path.join(s, "%s" % filename ))
             list_for_cpio.append(filename)