Systemd service-name does not respect variant `name` option

[brocaar]

I have a similar use-case as #86. I have one package for which I would like to distribute two versions. Example:

    [package.metadata.deb.variants.postgres]
      name = "example"

    [package.metadata.deb.variants.sqlite]
      example = "example-sqlite"

This correctly generates two .deb packages named:

• example and
• example-sqlite

However, it generates two systemd services:

• example-postgres
• example-sqlite

Expected behavor:

I would expect example and example-sqlite as systemd service-names.