ansible-lint: don't compare to empty string [E602] (#4665)

.ansible-lint

contrib/vault/roles/vault/tasks/shared/sync_file.yml

roles/container-engine/docker/tasks/set_facts_dns.yml

roles/download/tasks/set_docker_image_facts.yml

...tes-apps/cloud_controller/oci/tasks/credentials-check.yml

roles/kubernetes-apps/helm/tasks/main.yml

roles/kubernetes-apps/registry/tasks/main.yml

roles/kubernetes/node/tasks/azure-credential-check.yml

roles/kubernetes/node/tasks/main.yml

roles/kubernetes/node/tasks/openstack-credential-check.yml

roles/kubernetes/node/tasks/vsphere-credential-check.yml

roles/kubernetes/preinstall/tasks/0010-swapoff.yml

roles/kubernetes/preinstall/tasks/0020-verify-settings.yml

roles/kubernetes/tokens/tasks/gen_tokens.yml

roles/network_plugin/calico/tasks/check.yml

roles/upgrade/pre-upgrade/tasks/main.yml

tests/testcases/040_check-network-adv.yml