Namespace GlobalLocks to storage namespaces

Summary:
Currently, multiple unit tests that acquire global locks will interfere with each other. Namespace the locks so they don't.

(Possibly we should also rename this to PhabricatorStorageNamespaceLock or something since it's not really global any more, but that's kind of unwieldy...)

Test Plan: Acquired locks with --trace and verified they were namespaced properly.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T1162

Differential Revision: https://secure.phabricator.com/D2939