Fix the SCRIPT_DIR reference in integration tests.

[orsenthil]

There was an inconsistent usage of SCRIPT_DIR reference in the scripts directory.
That's why with the previous bug, only integration tests were successful and rest of the tests in the pipeline were failing.

Made sure that Integration tests use the correct reference too.

Testing Done

 ./scripts/run-integration-tests.sh
Testing git repository at commit 6e7b18538f5c79b19feff1913fc69e3bebeaad6b
"xxx"
Logging in to docker repo
WARNING! Your password will be stored unencrypted in /home/ec2-user/.docker/config.json.
Configure a credential helper to remove this warning. See
https://docs.docker.com/engine/reference/commandline/login/#credentials-store

Login Succeeded
Ensuring that amazon-k8s-cni exists for account xxx
creating ECR repo with name amazon-k8s-cni in registry account xxx
..
Ensuring that amazon-k8s-cni-init exists for account xxx
creating ECR repo with name amazon-k8s-cni-init in registry account xxx
...
Image amazon-k8s-cni:6e7b18538f5c79b19feff1913fc69e3bebeaad6b does not exist in repository.
docker buildx build --build-arg golang_image="public.ecr.aws/eks-distro-build-tooling/
...

[jaydeokar]

lgtm