kubeadm preflight: check CRI socket path if defined or docker service otherwise

[taharah]

What this PR does / why we need it:

Currently, running kubeadm init without Docker installed will cause the Service-Docker preflight check to fail even when another CRI is installed and the CRI socket specified. This changes the preflight checks to check the CRI socket if specified, and falling back to checking the Docker service otherwise. Additionally, this deduplicates common checks between kubeadm init and kubeadm join to ensure that similar preflight checks stay in-sync going forward.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes # kubernetes/kubeadm#657 - it still has the same behavior on joins
Fixes # kubernetes/kubeadm#749 - will check the CRI socket if specified and skip the Docker service check

Special notes for your reviewer:

Release note:

kubeadm preflight: check CRI socket path if defined, otherwise check for Docker

[taharah]

/assign @timothysc

[timothysc]

I'll do a pass, but I would also like feedback from

/cc @runcom

[runcom]

Looks ok to me, thanks for taking this one

[timothysc]

/lgtm
/approve

[taharah]

Thinking about this a little more, I am currently checking if the socket is defined at all, which it will always be since it will take the default of /var/run/dockershim.sock if it's not defined. Thus, I am going to amend the commit to check that the socket defined is not equal to the default rather than defined at all.

[taharah]

@timothysc and @runcom I added some additional deduplication of the checks that were common for both the kubeadm init and kubeadm join commands as well as changed to checking if the CRISocket defined is the default or not rather than simply checking if it has been defined at all.

[taharah]

/retest

[k8s-ci-robot]

@taharah: you can't request testing unless you are a kubernetes member.

In response to this:

/retest

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[xiangpengzhao]

/ok-to-test

[xiangpengzhao]

Hi @timothysc , I notice that you manually removed needs-ok-to-test label in this PR and others. However, manually remove this label doesn't make the PR trusted. (A trusted PR in test-infra means that it can be retested when author push new changes to the PR.) Only commenting /ok-to-test can make a PR trusted (and remove the label) so I suggest you remove the label by commenting :)

[taharah]

@timothysc or @xiangpengzhao this PR should be good to be merged now.

[0xmichalis]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kargakis, taharah, timothysc

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• cmd/kubeadm/OWNERS [timothysc]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[taharah]

/retest

[k8s-github-robot]

Automatic merge from submit-queue (batch tested with PRs 62481, 62643, 61877, 62515). If you want to cherry-pick this change to another branch, please follow the instructions here.