allow ingress addon for docker/podman drivers only on linux for now

[medyagh]

does not close #7332 but it will at least provide a better message.

after this PR:

💡  Due to docker networking limitations on darwin, ingress addon is not supported for this driver.
Alternatively to use this addon you can use a vm-based driver:

        'minikube start --vm=true'

To track the update on this work in progress feature please check:
https://github.com/kubernetes/minikube/issues/7332```

also add docs to the website

meanwhile we will work on implementing this feature for mac an windows.

[k8s-ci-robot]

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[medyagh]

/ok-to-test

[minikube-pr-bot]

Error: running mkcmp: exit status 1

[codecov-io]

Codecov Report

Merging #7393 into master will decrease coverage by 0.02%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #7393      +/-   ##
==========================================
- Coverage   37.16%   37.14%   -0.03%     
==========================================
  Files         146      146              
  Lines        8838     8844       +6     
==========================================
  Hits         3285     3285              
- Misses       5165     5170       +5     
- Partials      388      389       +1     

Impacted Files	Coverage Δ
pkg/addons/addons.go	43.60% <0.00%> (-1.58%)	⬇️

[minikube-pr-bot]

All Times Minikube (PR 7393): [ 62.167569 65.501514 64.078250]
All Times minikube: [ 62.892773 62.894432 64.539034]

Average minikube: 63.442080
Average Minikube (PR 7393): 63.915778

Averages Time Per Log

+----------------------+-----------+--------------------+
|         LOG          | MINIKUBE  | MINIKUBE (PR 7393) |
+----------------------+-----------+--------------------+
| minikube v           |  0.220317 |           0.213715 |
| Creating kvm2        | 39.824513 |          40.382699 |
| Preparing Kubernetes | 21.841580 |          21.643365 |
| Pulling images       |           |                    |
| Launching Kubernetes |           |                    |
| Waiting for cluster  |           |                    |
+----------------------+-----------+--------------------+

[reneli5]

I had the same issue using minikube and docker driver on my Mac. I deleted the docker profile and used the virtual box driver. All worked.
Here is how:

1. minikube delete
2. minikube start --vm-driver virtualbox
3. minikube addons enable ingress

[fzyzcjy]

Will ingress + docker be supported in the future? Thanks!