Use fingerprint during validation instead of identity file

[dazzrpm]

Always throws "Could not add to ssh-agent" error every generation of certificate even though it is successful and it's also not removing the old one.

Identity_file location (~/.ssh/blessid) is being searched on the the result of ssh-add -i instead of its fingerprint. This changes will use ssh-keygen -lf <identity_file> to get the finger print value of the identity file and use it to check if it's already existing on the ssh agent.