fixed apt-get

I have been getting a lot of:

Err http://us-east-1.ec2.archive.ubuntu.com/ubuntu/ raring/main librtmp-dev amd64 2.4+20111222.git4e06e21-1ubuntu1
  403  Forbidden
Failed to fetch http://us-east-1.ec2.archive.ubuntu.com/ubuntu/pool/main/k/krb5/libgssrpc4_1.10.1+dfsg-4+nmu1_amd64.deb  403  Forbidden

The past two days. Would you consider something like to following to resolve this issue?

I am uncomfortable about changing the source list behind the scenes but I don't think having to configure source list options is really in line with the it just works behavior that I like about starcluster.

Suggestions are welcome.