code.google.com/p/go.crypto/ssh is now at golang.org/x/crypto/ssh as of
https://code.google.com/p/go/source/detail?spec=svn.crypto.69e2a90ed92d03812364aeb947b7068dc42e561e&repo=crypto&r=8fec09c61d5d66f460d227fd1df3473d7e015bc6

Using the code.google.com import redirects properly, but runs into
issues if you try to use a subpackage of `ssh`, e.g. `agent` which
refers to golang.org/x/crypto/ssh causing conflicts if your types expect
code.google.com/p/go.crypto/ssh.

This is a precursor to a PR for #1066.