Change tunnel cleanup flag default to true for auto tunnel cleanup

[govargo]

What type of PR is this?

/kind feature

What this PR does / why we need it:

This PR change minikube tunnel's cleanup flag default to true.
Before this PR, if users have problem(like conflict) with minikube tunnel, users had to execute minikube tunnel --cleanup manually.
After this PR, minikube tunnel auto cleanup those error something.

Which issue(s) this PR fixes:

Fix #7900

Does this PR introduce a user-facing change?

Yes. This PR change minikube tunnel default behavior.

Before this PR

2 step is needed.

# 1. minikube tunnel has an error
$ minikube tunnel
Status:	
	machine: minikube
	pid: 764782
	route: 10.96.0.0/12 -> 172.17.0.2
	minikube: Running
	services: []
    errors: 
		minikube: no errors
		router: conflicting route: 10.96.0.0/12 via 172.17.0.3 dev docker0 
		loadbalancer emulator: no errors

# 2. cleanup manually
$ minikube tunnel --cleanup

After this PR

# 1. minikube tunnel clenup automatically
$ minikube tunnel
Status:	
	machine: minikube
	pid: 764782
	route: 10.96.0.0/12 -> 172.17.0.2
	minikube: Running
	services: []
    errors: 
		minikube: no errors
		router: no errors
		loadbalancer emulator: no errors

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

NONE

[k8s-ci-robot]

Hi @govargo. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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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.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: govargo
To complete the pull request process, please assign afbjorklund
You can assign the PR to them by writing /assign @afbjorklund in a comment when ready.

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

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[govargo]

/assign @afbjorklund

[minikube-bot]

Can one of the admins verify this patch?

[codecov-io]

Codecov Report

Merging #7946 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #7946   +/-   ##
=======================================
  Coverage   35.71%   35.71%           
=======================================
  Files         149      149           
  Lines        9408     9407    -1     
=======================================
  Hits         3360     3360           
+ Misses       5644     5643    -1     
  Partials      404      404           

Impacted Files	Coverage Δ
cmd/minikube/cmd/tunnel.go	5.26% <100.00%> (+0.13%)	⬆️

[medyagh]

/ok-to-test

[minikube-pr-bot]

kvm2 Driver
docker Driver