Problem: After thread context cloning was introduced in https://github.com/theforeman/foreman/pull/4653, it did not take into account any properties that could be added by plugins.
This would mean that if a plugin adds some properties to thread context, this context would not be available in the newly created thread, even after the context was cloned.

Solution: Put all thread-specific specific info in a single hash, and clone it to each thread that needs the context.
More detailed explanation can be found in original PR's comment: https://github.com/theforeman/foreman/pull/4653#discussion_r128525533.