Improve insecure registry validation

[kadern0]

Fixes 8790

Since some people complained about port being mandatory, I've decided to update the code to mimic docker's own validation.

Original discussion here.

Please se bellow the output for different insecure registries specifications:
Incorrect:

./out/minikube start --driver=docker --profile=testing3 --insecure-registry=:
😄  [testing3] minikube v1.13.0 on Ubuntu 20.04
✨  Using the docker driver based on user configuration
🎉  minikube 1.17.1 is available! Download it: https://github.com/kubernetes/minikube/releases/tag/v1.17.1
💡  To disable this notice, run: 'minikube config set WantUpdateNotification false'


❌  Exiting due to MK_USAGE: Sorry, the address provided with the --insecure-registry flag is invalid: :. Expected formtas are: <ip>[:<port>], <hostname>[:<port>] or <network>/<netmask>

$ ./out/minikube start --driver=docker --profile=testing3 --insecure-registry=127.0.0.1:
😄  [testing3] minikube v1.13.0 on Ubuntu 20.04
✨  Using the docker driver based on user configuration

❌  Exiting due to MK_USAGE: Sorry, the address provided with the --insecure-registry flag is invalid: 127.0.0.1:. Expected formtas are: <ip>[:<port>], <hostname>[:<port>] or <network>/<netmask>

$ ./out/minikube start --driver=docker --profile=testing3 --insecure-registry=svn://mytest.com
😄  [testing3] minikube v1.13.0 on Ubuntu 20.04
✨  Using the docker driver based on user configuration

❌  Exiting due to MK_USAGE: Sorry, the address provided with the --insecure-registry flag is invalid: svn://mytest.com. Expected formtas are: <ip>[:<port>], <hostname>[:<port>] or <network>/<netmask>

$ ./out/minikube start --driver=docker --profile=testing3 --insecure-registry=1200:0000:AB00:1234:0000:2552:7777:1313:8080
😄  [testing3] minikube v1.13.0 on Ubuntu 20.04
✨  Using the docker driver based on user configuration

❌  Exiting due to MK_USAGE: Sorry, the address provided with the --insecure-registry flag is invalid: 1200:0000:AB00:1234:0000:2552:7777:1313:8080. Expected formtas are: <ip>[:<port>], <hostname>[:<port>] or <network>/<netmask>

$ ./out/minikube start --driver=docker --profile=testing3 --insecure-registry=mytest.com:500000
😄  [testing3] minikube v1.13.0 on Ubuntu 20.04
✨  Using the docker driver based on user configuration

❌  Exiting due to MK_USAGE: Sorry, the address provided with the --insecure-registry flag is invalid: mytest.com:500000. Expected formtas are: <ip>[:<port>], <hostname>[:<port>] or <network>/<netmask>

$ ./out/minikube start --driver=docker --profile=testing3 --insecure-registry=-mytest.com
😄  [testing3] minikube v1.13.0 on Ubuntu 20.04
✨  Using the docker driver based on user configuration

❌  Exiting due to MK_USAGE: Sorry, the address provided with the --insecure-registry flag is invalid: -mytest.com. Expected formtas are: <ip>[:<port>], <hostname>[:<port>] or <network>/<netmask>

Correct:

$ ./out/minikube start --driver=docker --profile=testing3 --insecure-registry=172.16.32.24
😄  [testing3] minikube v1.13.0 on Ubuntu 20.04
✨  Using the docker driver based on user configuration
👍  Starting control plane node testing3 in cluster testing3
🔥  Creating docker container (CPUs=2, Memory=3900MB) ...

$ ./out/minikube start --driver=docker --profile=testing3 --insecure-registry=172.16.32.24
😄  [testing3] minikube v1.13.0 on Ubuntu 20.04
✨  Using the docker driver based on existing profile
👍  Starting control plane node testing3 in cluster testing3


$ ./out/minikube start --driver=docker --profile=testing3 --insecure-registry=172.16.32.24:8080
😄  [testing3] minikube v1.13.0 on Ubuntu 20.04
✨  Using the docker driver based on user configuration
👍  Starting control plane node testing3 in cluster testing3
🔥  Creating docker container (CPUs=2, Memory=3900MB) ...


$ ./out/minikube start --driver=docker --profile=testing3 --insecure-registry=2001:db8::1
😄  [testing3] minikube v1.13.0 on Ubuntu 20.04
✨  Using the docker driver based on user configuration
👍  Starting control plane node testing3 in cluster testing3
🔥  Creating docker container (CPUs=2, Memory=3900MB) ...
^C

$ ./out/minikube start --driver=docker --profile=testing3 --insecure-registry=[2001:db8::1]:80
😄  [testing3] minikube v1.13.0 on Ubuntu 20.04
✨  Using the docker driver based on user configuration
👍  Starting control plane node testing3 in cluster testing3
🔥  Creating docker container (CPUs=2, Memory=3900MB) ...


$ ./out/minikube start --driver=docker --profile=testing3 --insecure-registry=https://mytest.com:80
😄  [testing3] minikube v1.13.0 on Ubuntu 20.04
✨  Using the docker driver based on user configuration
👍  Starting control plane node testing3 in cluster testing3
🔥  Creating docker container (CPUs=2, Memory=3900MB) ...

[k8s-ci-robot]

Hi @kadern0. 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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[minikube-bot]

Can one of the admins verify this patch?

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kadern0, medyagh

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[medyagh]

thank you for improving this @kadern0