(SERVER-30) Improve SSL fail-fast for master & CA

The first change in here adds fail-fast behavior to the master service so that it will fail to start if it finds it doesn't have its private key, certificate, and local CA certificate.  If all three of those files are missing, the entire set of SSL files will be generated.

The second change in here loosens the conditions for CA fail-fast so it no longer requires the CA public key, and it will automatically create the signed/ and requests/ directories if they don't exist.
Yeah, I wish I had a `master-sandbox!` function like we do for the CA stuff, but didn't know how much time I should spend refactoring the tests again.  I'd be happy to clean this up if others think that's worthwhile.