Multiple references to same privkey = key multiply loaded by agent

[Tabiskabis]

I have two different certificates (signed by different CAs) stored in Windows personal certstore, that refer to the same private key stored on a YubiKey.
This results in the private key being referenced and loaded twice by WinCryptSSHAgent, which is not a problem per se, but superfluous.
It only occured to me because it pushes the number of available private keys in the agent over Debians default "MaxAuthTries", so when i try to SSH into a Debian machine, the connection fails (unless i remove one key from the Agent or specify a pubkey file for ssh to use)

[Tabiskabis]

probably the same issue: #64