[stable/sonarqube] Fix failing deployment and tests

[rjkernick]

What this PR does / why we need it:

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

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[rjkernick]

/assign unguiculus

[unguiculus]

/ok-to-test

[unguiculus]

/lgtm

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[jcscottiii]

@rjkernick Which version of k8s are you using?
When I was on 1.8.x, this PR worked fine for me.
Last night, I decided to update our cluster to 1.9.6 and this deployment broke. I kept getting Read-Only errors. Did some digging and found out that it was related to this security patch kubernetes/kubernetes#60814

Tried this PR #4787 out but it didn't work. But if i revert this patch and make the following change, it works.

@@ -115,6 +114,7 @@ spec:
           name: {{ template "sonarqube.fullname" . }}-config
       - name: install-plugins
         configMap:
+          defaultMode: 0755
           name: {{ template "sonarqube.fullname" . }}-install-plugins

But yeah, just wanted to gauge how's everything working on your side.

Examples of other charts having this problem:
#4272
#4166

[rjkernick]

I am on 1.8.x, but have also tested it on minikube with 1.9.4. I believe the helm tests run against 1.9.x as well