Enable retry for Ubuntu installs

This is a proactive solution to bug
1355347, which allows retries for failed
downloads of packages from apt mirror
during installation.

Change-Id: I848a86ef27f9ad8235024996b7417a30689daa4f
Partial-Bug: #1355347

deployment/puppet/cobbler/templates/preseed/ubuntu-1204.preseed.erb

@@ -48,7 +48,10 @@ d-i mirror/suite string precise
 d-i mirror/udeb/suite string precise
 # Components to use for loading installer components (optional).
 d-i mirror/udeb/components multiselect main, restricted
-
+# Retry failed repo
+d-i apt-setup/mirror/error select Retry
+# Downloading a file failed
+# d-i apt-setup/use_mirror select Retry
 
 d-i apt-setup/restricted boolean true
 d-i apt-setup/universe boolean true