ssh: Move shared code from ~/.profile.d -> ~/lib/bash/kiwi/ssh.bash

This patch creates a new bash library, '~/lib/bash/kiwi/ssh.bash', that
contains the core logic from '~/.profile.d/40-ssh.sh`. This will enable
git hooks and other shell scripts to reuse the code that was in
'~/.profile.d/40-ssh.sh'.

Tags: public
ssh: Rename vars from SSH namespace into kw_ssh namespace

Tags: public
ssh: Don't print old ssh-agent info

In the message that kw_ssh_start_agent() prints after starting the
agent, it printed info for the *old* agent. Fix it to print info for the
*current* agent.

Tags: public