Configure reactor on Salt primary server

Summary:
To make easier to track what events should use what reactor SLS file,
the reactor configuration file is to be published on this repository.

Therefore, the configuration consists of a symlink to that file.

Ref T1942

Test Plan:

• mkdir reactor ; touch reactor/reactor.conf
• deploy state, symlink is created
• rm reactor/reactor.conf
• deploy state, symlink is deleted

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1942

Differential Revision: https://devcentral.nasqueron.org/D3279