Key loading incorrect with ssh-agent 7.7p1 on Windows

[russjones]

We've gotten reports that ssh-agent on Windows from OpenSSH 7.7p1 does not load keys correctly.

The issue is that that when tsh is loading keys into an agent, it adds the certificate first then the key. With this version of ssh-agent on Windows, the key overrides the certificate because they have the same name. A proposed solution is to reverse the order, add the key, then the certificate. This would maintain backward compatibility with OpenSSH 7.3/7.3p1 (which is the reason why tsh loads the key and certificate into the agent) by having both the key and certificate in the agent as well as be compatibly with OpenSSH for Windows.

I tried to reproduce this issue with openssh-portable on Linux and could not.

This can probably be addressed at the same time as #1996.

[russjones]

Fixed in #2128.