When running in CI system (no TTY) give up on passphrase

[dhiltgen]

When running in a CI system where no TTY is attached, if something goes wrong, notary winds up asking for a root pass phrase over and over without end. We recently had our CI system run out of disk space due to gig's of logs with the repeating pattern:

Enter passphrase for new root key with ID fdd4003: 
Enter passphrase for new root key with ID fdd4003: 
Enter passphrase for new root key with ID fdd4003: 

Notary should be smarter and give up asking for a passphrase when there's no tty instead of looping.

[endophage]

It should give up after 10(?) retries. But if enabled, the password should be in the environment anyway.

i.e. Either there should be a password, or it shouldn't be enabled. If you're running in some other configuration it would be useful to us to understand what the use case is.

[endophage]

Ok, there's a bug with the 10 retries that I thought had been fixed so we've moved this issue into scope #812

We'll also take a look at detecting if there's no terminal attached.

[dhiltgen]

The scenario where I hit this was using delegation and I forgot to add the delegation key to a new repository that was created.