Pvt key provided - flow

Working notes on Pvt key provided - flow: 1. if key explicit, 1. Check serial with server, 1. Ok, 1. If passphrase, and 2. Else keys::PAgent.

1. if key explicit

1. Check serial with server

1. Ok

1. If passphrase

1. Ask.

2. Else keys::PAgent

1. Try each.