Config step shouldn't add tag if already exists

[cliffano]

Even though most users would run config once from the base CF template, it's possible that some users would run config against a pre-configured state, and it currently ends up adding a tag even if it already exists.

This is also a common scenario during development. When we're testing the configuration for various permutations of aem versions and os types, config ends up getting executed multiple times.

Need to add a check so a tag won't be added if it already exists.