Fixing rootfs re, currently we also have config.tar.gz (was bz2 in the past)

Signed-off-by: Ricardo Salveti de Araujo <ricardo.salveti@linaro.org>
diff --git a/crawler.py b/crawler.py
index de7679a..f67de21 100755
--- a/crawler.py
+++ b/crawler.py
@@ -51,7 +51,8 @@
     return hwpacks
 
 def list_rfs(url):
-    links = list_links(url, r'<a\s*href=[\'|"].*[\'"]>(.*\.tar\.gz)</a>')
+    links = list_links(url,
+       r'<a\s*href=[\'|"].*[\'"]>(.*\-\d+\.(?!config)(?:rootfs\.)?tar\.gz)</a>')
     if len(links) is 1:
         return "%s/%s" %(url,links[0])
     return None