Update templates used with mercurial to remove '--debug'

Summary:
Refs D21679 (phabricator changes)

This updates Arcanist to be able to check whether the version of Mercurial supports using {p1.node} template format vs. {p1node}.

Test Plan: Tested under coverage from D21679

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D21681