Issue converting Munki Conditions to a string

```
2020-09-24 17:01:49,357 INFO Processing checkin modules...
Traceback (most recent call last):
  File "/usr/local/sal/checkin_modules/munki_checkin.py", line 157, in <module>
    main()
  File "/usr/local/sal/checkin_modules/munki_checkin.py", line 42, in main
    value = ', '.join(value)
TypeError: sequence item 0: expected str instance, dict found
```