title: Jenkins ssh agent plugin is getting stacked, No error, no timeout issue
body: <p>I installed <strong>jenkins ssh agent plugin</strong>. I created ssh private key on the linux server(using <strong>ssh-keygen -t rsa</strong> command) I am trying to connect. Then under jenkins credintials added <strong>SSH Username with private key</strong> with all required fields. In jenkinsfile added simple command to run over ssh:</p>
  
  <pre><code>pipeline {
     agent any
     stages {
         stage('---doingsomething---') {
              steps {
                  sshagent (credentials: ['jbowner-195']) {
                      sh 'ssh -o StrictHostKeyChecking=no -l jbowner 10.10.23.195 uname -a'
                  }
              }
         }
  
     }
  }
  </code></pre>
  
  <p>When I press build button process is starting and never ending. No error, no timeout issue.
  Here is piece of output on which jenkins stacks</p>
  
  <pre><code>[Pipeline] }
  [Pipeline] // stage
  [Pipeline] withEnv
  [Pipeline] {
  [Pipeline] stage
  [Pipeline] { (---echoing---)
  [Pipeline] sshagent
  [ssh-agent] Using credentials jbowner (jbowner 10.10.23.195)
  [ssh-agent] Looking for ssh-agent implementation...
  [ssh-agent]   Exec ssh-agent (binary ssh-agent on a remote machine)
  $ ssh-agent
  SSH_AUTH_SOCK=/tmp/ssh-XSQPEUHOqZQR/agent.10226
  SSH_AGENT_PID=10229
  Running ssh-add (command line suppressed)
  Identity added: /home/jenkins/.jenkins/workspace/Eformgenerator-Prod@tmp/private_key_5151715321960722060.key (/home/jenkins/.jenkins/workspace/Eformgenerator-Prod@tmp/private_key_5151715321960722060.key)
  [ssh-agent] Started.
  [Pipeline] {
  [Pipeline] sh
  + ssh -o StrictHostKeyChecking=no -l jbowner 10.10.23.195 uname -a
  </code></pre>
  
  <p>any ideas?</p>