Role fails when using a vault-encrypted token variable

[dale-c-anderson]

The check for the token in tasks/main.yml produces the following error if gitlab_runner_registration_token is encrypted with ansible vault:

object of type 'AnsibleVaultEncryptedUnicode' has no len()

According to ansible/ansible#33067, it looks like we can just throw a |string in there to work around it. I'll submit a PR.

[riemers]

Sounds like a plan!