fix virtualbox IP address retrieval

[sharifelgamal]

Based on #8083

Thanks to @cprogrammer1994 for finding and fixing the issue initially.

Fixes #7993

Before

* minikube v1.10.0 on Microsoft Windows 10 Pro 10.0.18363 Build 18363
* Using the virtualbox driver based on user configuration
* Starting control plane node minikube in cluster minikube
* Creating virtualbox VM (CPUs=2, Memory=6000MB, Disk=20000MB) ...
* Preparing Kubernetes v1.18.1 on Docker 19.03.8 ...
E0512 16:21:31.787931   15788 start.go:95] Unable to get host IP: Error getting VM/Host IP address: Error finding IPV4 address for VirtualBox Host-Only Ethernet Adapter #2
*
X failed to start node: startup failed: Failed to setup kubeconfig: Error getting VM/Host IP address: Error finding IPV4 address for VirtualBox Host-Only Ethernet Adapter #2
*
* minikube is exiting due to an error. If the above message is not useful, open an issue:
  - https://github.com/kubernetes/minikube/issues/new/choose

After

* minikube v1.10.0 on Microsoft Windows 10 Pro 10.0.18363 Build 18363
* Using the virtualbox driver based on user configuration
* Starting control plane node minikube in cluster minikube
* Creating virtualbox VM (CPUs=2, Memory=6000MB, Disk=20000MB) ...
* Preparing Kubernetes v1.18.1 on Docker 19.03.8 ...
* Verifying Kubernetes components...
* Enabled addons: default-storageclass, storage-provisioner
* Done! kubectl is now configured to use "minikube"

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sharifelgamal

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[medyagh]

/ok-to-test

[minikube-pr-bot]

kvm2 Driver
docker Driver

[codecov-io]

Codecov Report

Merging #8106 into master will decrease coverage by 0.07%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #8106      +/-   ##
==========================================
- Coverage   35.35%   35.27%   -0.08%     
==========================================
  Files         146      146              
  Lines        9321     9326       +5     
==========================================
- Hits         3295     3290       -5     
- Misses       5627     5637      +10     
  Partials      399      399              

Impacted Files	Coverage Δ
pkg/minikube/cluster/ip.go	0.00% <0.00%> (ø)
pkg/minikube/machine/delete.go	33.92% <0.00%> (-11.36%)	⬇️