[IMPROVEMENT] reported state changes on new/added zone are confusing

Description
The changes reported when a new zone is created/added are confusing because the new key is simply set to the new zone's name instead of the existing zones with the new zone's name added to it (see code reference below). This way one gets the impression that the new zone replaced the existing ones (as in zone-pruning).

Setup
Version: Salt: 3006.7

Relevant line of code: here

Steps to Reproduce the behavior
Create a new zone using firewalld.present with (say, two) other zones already existing.

Expected behavior

     Changes:
              new-zone:
                  ----------
                  new:
                      - existing-zone1
                      - existing-zone2
                      - new-zone
                  old:
                      - existing-zone1
                      - existing-zone2

Actual behavior

     Changes:
              new-zone:
                  ----------
                  new:
                      - new-zone
                  old:
                      - existing-zone1
                      - existing-zone2

Thanks

Start at salt/states/firewalld.py around line 419 and reproduce the behavior with firewalld.present while two existing zones are present. Compare the reported new and old zone lists with the expected output; done means the new list includes the existing zones plus the newly added zone.