Allow 'profiles list' to work even if a profile has no control plane

[tstromberg]

Fixes bug seen in #6409 integration test.

Libraries should never cause fatal exits.

[k8s-ci-robot]

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[tstromberg]

/ok-to-test

[codecov-io]

Codecov Report

Merging #6450 into master will increase coverage by 0.01%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #6450      +/-   ##
==========================================
+ Coverage   37.68%   37.69%   +0.01%     
==========================================
  Files         128      128              
  Lines        8654     8674      +20     
==========================================
+ Hits         3261     3270       +9     
- Misses       4970     4979       +9     
- Partials      423      425       +2

Impacted Files	Coverage Δ
cmd/minikube/cmd/config/profile_list.go	3.94% <0%> (ø)	⬆️
cmd/minikube/cmd/delete.go	27.41% <0%> (-1.02%)	⬇️
pkg/minikube/cluster/cluster.go	37.59% <0%> (-0.68%)	⬇️
pkg/minikube/config/profile.go	69.29% <0%> (+1.97%)	⬆️

[tstromberg]

I confirmed this works to display nodes created with older releases of minikube.

E0131 14:43:00.246474   61424 profile_list.go:85] "vupgrade-20200131T144125.325621-58653" has no control plane: could not find master node
|-------------------------------------------|------------|----------------|-----------|--------------------|---------|
|                  Profile                  | VM Driver  |     NodeIP     | Node Port | Kubernetes Version | Status  |
|-------------------------------------------|------------|----------------|-----------|--------------------|---------|
| containerd-20200131T144125.32588-58653    | virtualbox |                |      8444 | v1.17.2            |         |
| crio-20200131T144125.326867-58653         | virtualbox | 192.168.99.253 |      8443 | v1.15.7            | Running |
| docker-flags-20200131T144125.325604-58653 | virtualbox |                |      8443 | v1.17.2            |         |
| functional-20200131T143927.684822-58653   | virtualbox | 192.168.99.247 |      8443 | v1.17.2            | Running |
| newest-cni-20200131T144125.325885-58653   | virtualbox |                |      8443 | v1.17.2            |         |
| old-docker-20200131T144125.325738-58653   | virtualbox |                |      8443 | v1.11.10           | Running |
| vupgrade-20200131T144125.325621-58653     | virtualbox |                |         0 | v1.11.10           | Running |
|-------------------------------------------|------------|----------------|-----------|--------------------|---------|
⚠️  Found 1 invalid profile(s) ! 
	 minikube
💡  You can delete them using the following command(