Fix bugs that prevented previously-enabled addons from starting up

[tstromberg]

If a cluster is stopped, and then started, we were not enabling previously enabled addons due to two bugs:

• We were not reading the existing addons config
• Even if we were, the necessary directory (/etc/kubernetes/addons) was not being recreated at startup.

Fixes #6456

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: tstromberg

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[medyagh]

/ok-to-test

[minikube-pr-bot]

Error: running mkcmp: exit status 1

[minikube-pr-bot]

All Times minikube: [ 101.919553 95.012687 102.323714]
All Times Minikube (PR 6471): [ 100.270500 96.253887 97.864844]

Average minikube: 99.751984
Average Minikube (PR 6471): 98.129744

Averages Time Per Log

+----------------------+-----------+--------------------+
|         LOG          | MINIKUBE  | MINIKUBE (PR 6471) |
+----------------------+-----------+--------------------+
| minikube v           |  0.331211 |           0.327189 |
| Creating kvm2        | 20.373761 |          20.924098 |
| Preparing Kubernetes | 50.258178 |          49.512817 |
| Pulling images       |  4.155255 |           3.854587 |
| Launching Kubernetes | 21.297202 |          19.879988 |
| Waiting for cluster  |  1.070253 |           1.086055 |
+----------------------+-----------+--------------------+

[codecov-io]

Codecov Report

Merging #6471 into master will decrease coverage by 0.12%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #6471      +/-   ##
==========================================
- Coverage   37.99%   37.87%   -0.13%     
==========================================
  Files         128      128              
  Lines        8729     8757      +28     
==========================================
  Hits         3317     3317              
- Misses       4986     5014      +28     
  Partials      426      426

Impacted Files	Coverage Δ
cmd/minikube/cmd/delete.go	25.12% <0%> (-1.55%)	⬇️
cmd/minikube/cmd/stop.go	0% <0%> (ø)	⬆️
cmd/minikube/cmd/status.go	23.14% <0%> (-3.17%)	⬇️

[minikube-pr-bot]

All Times minikube: [ 99.983179 96.674863 102.425099]
All Times Minikube (PR 6471): [ 98.018484 101.017347 100.470089]

Average minikube: 99.694380
Average Minikube (PR 6471): 99.835307

Averages Time Per Log

+----------------------+-----------+--------------------+
|         LOG          | MINIKUBE  | MINIKUBE (PR 6471) |
+----------------------+-----------+--------------------+
| minikube v           |  0.453406 |           0.300249 |
| Creating kvm2        | 21.037232 |          20.459426 |
| Preparing Kubernetes | 50.891924 |          50.925354 |
| Pulling images       |  3.692811 |           3.435675 |
| Launching Kubernetes | 20.059037 |          21.251220 |
| Waiting for cluster  |  1.392061 |           1.068302 |
+----------------------+-----------+--------------------+

[minikube-pr-bot]

All Times minikube: [ 95.919006 97.562193 97.807202]
All Times Minikube (PR 6471): [ 96.293574 96.471989 97.442563]

Average minikube: 97.096134
Average Minikube (PR 6471): 96.736042

Averages Time Per Log

+----------------------+-----------+--------------------+
|         LOG          | MINIKUBE  | MINIKUBE (PR 6471) |
+----------------------+-----------+--------------------+
| minikube v           |  0.313105 |           0.306181 |
| Creating kvm2        | 20.206672 |          20.202842 |
| Preparing Kubernetes | 49.396775 |          49.961816 |
| Pulling images       |  4.324972 |           3.748858 |
| Launching Kubernetes | 19.205640 |          19.532199 |
| Waiting for cluster  |  1.054114 |           1.079803 |
+----------------------+-----------+--------------------+