Summary: Minor updates to Drydock things to make them work better. In particular, after this patch working copies are correctly allocated or reused.
Test Plan: Ran "reparse.php --harbormaster <derp derp>", saw reuse of working copies when unleased resources were avilable.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T2015
Differential Revision: https://secure.phabricator.com/D4216
