Fixing lint errors in pkg/gcp

[nikhiljindal]

Fixes https://github.com/GoogleCloudPlatform/k8s-multicluster-ingress/issues/44

Ref #61

Fixing lint error for pkg/gcp

All sub packages in pkg/gcp have similar changes. The pattern was already reviewed for url map in https://github.com/GoogleCloudPlatform/k8s-multicluster-ingress/pull/180. Have hence combined all the changes in this single PR. Apologies if its too big and hard to review :)

cc @G-Harmon

[G-Harmon]

phew, that was long!

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Reviewed 22 of 22 files at r1. Review status: all files reviewed at latest revision, all discussions resolved.

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Comments from Reviewable

[nikhiljindal]

Thanks @G-Harmon :)