Ship plugin disk space fix in upstream jenkins image

[hrishin]

In order to reduce the plugins disk usage, we have symlinked plugins directory.
To switch upstream Jenkins OpenShift base (builder) image, we need to ship the plugins fix in the upstream image as well.

[chmouel]

👍 and i think we need to have an issue in upstream openshift/jenkins repository,

[piyush-garg]

Basically, we have added two fixes -

1. Symlink plugins instead of copying them fabric8-jenkins/jenkins-openshift-base#49
2. Improves plugin storage fix and reduces the image size fabric8-jenkins/jenkins-openshift-base#52

in our fork to fix the issues -

1. Optimise plugin disk space in Jenkins openshiftio/openshift.io#4568
2. Build: reduce the jenkins image size openshiftio/openshift.io#4635

We need to add these two fixes in upstream so that we can continue our efforts of moving to upstream images.

For this, we need to create an issue there, discuss with upstream folks how we can get it added there. Maybe we can add a flag, which if set, symlink the plugins in place of copying