Using GCE feature 'deploying-containers' fails because of missing Java on host

This plugin supports using [GCE instance templates](https://cloud.google.com/compute/docs/instance-templates/) for provisioning a new Jenkins SSH slave.

I created a new instance template in Google compute engine, which uses the GCE feature [deploy containers](https://cloud.google.com/compute/docs/containers/deploying-containers). As the _Container-image_, I am using openjdk:11-jre-slim.

When using this plugin, a new VM is booted up by my Jenkins job, but Jenkins master fails to connect to it.

From Jenkins log:
> May 03, 2019 9:13:31 AM INFO com.google.jenkins.plugins.computeengine.ComputeEngineCloud log
>
> Connecting to 35.209.XXX.YY on port 22, with timeout 10000.
>
> May 03, 2019 9:13:35 AM INFO com.google.jenkins.plugins.computeengine.ComputeEngineCloud log
>
> Connected via SSH.
>
> May 03, 2019 9:13:35 AM INFO com.google.jenkins.plugins.computeengine.ComputeEngineCloud log
>
> connect fresh as root
>
> May 03, 2019 9:13:35 AM INFO com.google.jenkins.plugins.computeengine.ComputeEngineCloud log
>
> Connecting to 35.209.254.68 on port 22, with timeout 10000.
>
> May 03, 2019 9:13:35 AM INFO com.google.jenkins.plugins.computeengine.ComputeEngineCloud log
>
> Connected via SSH.
>
> May 03, 2019 9:13:35 AM INFO com.google.jenkins.plugins.computeengine.ComputeEngineCloud log
>
> Copying agent.jar to: /tmp
>
> May 03, 2019 9:13:35 AM INFO com.google.jenkins.plugins.computeengine.ComputeEngineCloud log
>
> Verifying: java -fullversion
>
> May 03, 2019 9:13:35 AM WARNING com.google.jenkins.plugins.computeengine.ComputeEngineCloud log
>
> Java is not installed.

Well, this failure seems quite obvious to me. There is no Java installed on the machine/host with the (external) IP _35.209.XXX.YY_. There would be / is a docker image openjdk:11-jre-slim available on this machine, which could/should be used for executing Java.

Please let this plugin support the feature 'deploying-containers'

PS: This is a follow-up of https://issues.jenkins-ci.org/browse/JENKINS-52251