WIP: refresh pillar data on host update

[mattiasgiese-b1]

This PR is currently not finished and should not be merged. I want to start a discussion about how to integrate such a feature.
Our usecase:

We want to be able to use the Salt environment set in the hosts pillar data as the env for the minion. In order to do this we need
a little change in Salt (see saltstack/salt#60233) and a new command in the proxy plugin (see theforeman/smart_proxy_salt#65)

This works well, but now i hit a roadblock with the code in this PR. Because salt-master will run foreman-node (and therefor update the minions grains) it will trigger another host update, which in turn triggers a update of the hosts grains, resulting in an endless loop.
Is there any way to check whether the user has adjusted the Salt environment itself to only trigger the refresh of pillar data if that's the case?

[theforeman-bot]

Can one of the admins verify this patch?