Enable autotest client package fetching based on updated image.

server/site_autotest.py

Index: server/site_autotest.py
diff --git a/server/site_autotest.py b/server/site_autotest.py
index 1709b280fa61ce0543a2011876913ace2a950873..4b6671211cad9de0e5c2297c6b58ae8296deb3b4 100755
--- a/server/site_autotest.py
+++ b/server/site_autotest.py
@@ -1,5 +1,11 @@
 import os
-from autotest_lib.server import installable_object
+from autotest_lib.client.common_lib import global_config
+from autotest_lib.server import autoserv_parser, installable_object
+
+
+config = global_config.global_config
+parser = autoserv_parser.autoserv_parser
+
 
 class SiteAutotest(installable_object.InstallableObject):
 
@@ -11,5 +17,21 @@ class SiteAutotest(installable_object.InstallableObject):
         self.got = True
 
 
+    def get_fetch_location(self):
+        if not parser.options.image:
+            return super(SiteAutotest, self).get_fetch_location()
+
+        repos = config.get_config_value('PACKAGES', 'fetch_location', type=list,
+                                        default=[])
+        new_repos = []
+        for repo in repos[::-1]:
+            if repo.endswith('static/archive'):
+                path = parser.options.image.rstrip('/')
+                build = '/'.join(path.split('/')[-2:])
+                repo += '/%s/autotest' % build
+            new_repos.append(repo)
+        return new_repos
+
+
 class _SiteRun(object):
     pass