Change xdebug.max_nesting_level config after XDebug changes

Summary: Fixes T5027. XDebug has changed how it interprets `0`. See the task or inline for more discussion.

Test Plan:
  - @martin.lindhe confirmed this resolve issues locally.
  - Dug through XDebug to find a root cause for this behavior.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: martin.lindhe, epriestley

Maniphest Tasks: T5027

Differential Revision: https://secure.phabricator.com/D9075