Add missing default value to disable testing repo

[javierbertoli]

After mergin #45, the state fails to apply correctly, with the error:

Data failed to compile:
       ----------
           Rendering SLS 'base:epel' failed: Jinja variable 'dict object' has no attribute 'testing'

Pre-#45, the formula checked that parameter directly from the pillar, after the merge, it checks the parameter from map.jinja, where it does not exist. This PR adds the default value.

[noelmcloughlin]

Thanks for that.