Removed unnecessary EventHandler

Summary:
Reduced intitialisation overhead for Sherpa after review of Code with Marek in Durham.

This is related with !27 and T250.

Test Plan: Sherpa tests give identical outputs compared with master.

Reviewers: kreps, tlatham, jback

Reviewed By: tlatham

Differential Revision: https://phab.hepforge.org/D125