[BUG] salt.states.grains.list_present append already existing values

[dereckson]

Description
According the documentation, salt.states.grains.list_present should only add a value to a a grain formatted as a list if it doesn't exist.

It's possible to pass multiple grains, but then, if one of them isn't present, the full list is added, including already existing items.

Steps to Reproduce the behavior
A minimal repro case from the salt.states doc and an update:

server_roles:
  grains.list_present:
    - value:
      - web
      - dev

server_roles_one_more_time:
  grains.list_present:
    - name: server_roles
    - value:
      - web
      - mail
      - dev

Expected behavior
grain serve_roles should contain web, dev, mail, only once for web and dev

Versions Report
salt 3004.1, repro with salt-call --local