tags in different mixins don't merge

[lamdor]

If I have:

mixins:
   staging:
     tags:
       environment: staging
   hbase:
     tags:
       hbase: true

servers:
  example:
    mixins: [staging, hbase]

when I do a knife whisk generate example, the tags part isn't merged and is outputted as a ruby hash, not the knife ec2 server create --tags format.