Drop Windows-specific escaping in preallocated host

Summary: This drops the Windows-specific escaping code for the creation of directories when acquiring a lease. This is basically the change from D10378 without the other, no longer necessary changes.

Test Plan: This code hasn't been run in a production environment for a while (any instances of Phabricator using Drydock / Harbormaster with Windows have had this code removed by the D10378 patch for a while).

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Projects: #drydock

Differential Revision: https://secure.phabricator.com/D13341