fix: kubectl with gke-gcloud-auth-plugin, unbound variable

[tino415]

Remove forcing all variables to be bound in shell scripts that are run when gcloud commands are executed

Description

Remove set -u option from scripts executed when gcloud commands are executed to support commands without arguments for instance gke-gcloud-auth-plugin

Motivation and Context

gcloud kubectl was not working because it is using command without argument under the hood. It fixes this issue

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Usage examples

kubectl get pods without error.

How Has This Been Tested?

Installed locally and tried to run kubectl get pods

Checklist:

• [x] I have updated the documentation accordingly.
• [ ] I have added tests to cover my changes.

[sodabrew]

+1 this worked for me, too. (comment edit: removed red herring alternative suggestion)