Various linter fixes

Summary:
Fixed various linter issues that were identified by running `arc lint --everything`.

- Removed trailing whitespace.
- Added newline at EOF.
- Added whitespace after `if` statement

Test Plan: N/A

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: aurelijus, Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D8337
Merge branch 'master' of http://github.com/facebook/arcanist