Incorrect checks for ssh-agent in util.sh results in improper *pem key addition

[bluerider]

The check for util.sh counts the number of global ssh-agent PID (this includes other users) instead of checking to see if ssh-agent environmental variables are properly set. This means that other users running ssh-agent or even if the same user has a running ssh-agent instance but no authentication to the ssh-agent socket will not trigger an error in the util.sh code.