Use REPO plugin with ssh-agent plugin to repo init failed if passphrase is not empty.

Steps:

1. Use ssh-keygen to generate public/private rsa key pair, and enter passphrase;

2. Add Credentials in Jenkins named 'phoebus', fill private key and passphrase. Fill public key to Gerrit.

3. Create a Job, use Gerrit Repo as Source Code Management, the Manifest Repository Url is ssh://phoebus@ubuntu:29418/platform/manifest, and SSH Agent-> Credentials chose 'phoebus';

3. Build failed, the Console Output is as follows:

 
Building in workspace /var/lib/jenkins/workspace/demo-repo
[ssh-agent] Using credentials phoebus
[ssh-agent] Looking for ssh-agent implementation...
[ssh-agent]   Java/JNR ssh-agent
[ssh-agent] Started.
[demo-repo] $ repo init -u ssh://phoebus@ubuntu:29418/platform/manifest
Get ssh://phoebus@ubuntu:29418/platform/manifest
Permission denied (publickey).
Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

BTW, I try to create a new job and use Git Plugin to clone ssh://phoebus@ubuntu:29418/platform/manifest, it is successful.