Add check that service tag isn't in path name

This commit adds a new hacking check to ensure that a service tag
isn't added on a test whose path includes the service tag being added.
Having a service tag added where the path already contains the service
name is redundant.

Partially implements bp add-service-tags

Change-Id: I88b3005d05e17751045d766efb1e965822a3c50e
Merge "Add check that service tag isn't in path name"