label_check outputs duplicates

See the label_check portion of this pipeline as an example: https://repo1.dso.mil/platform-one/big-bang/bigbang/-/jobs/12709518

Notice:

Initial MR labels: metricsServer,metricsServer 
Evaluating package dependencies...
Labels after check: metricsServer,metricsServer

We should ensure that these lists are "uniq-ified" before printing and passing along to other stages. Otherwise you end up with the pipeline outputting:

⏳ Checking if metrics-server HR is enabled
metrics-server HR is enabled, waiting...
⏳ Checking if metrics-server HR is enabled
metrics-server HR is enabled, waiting...