R1:c0cc7bbfdfd3

Provide `bin/auth ldap` for LDAP diagnostics

Summary: Ref T1536.

Test Plan: Ran `bin/auth ldap`.

Reviewers: mbishopim3, chad

Reviewed By: mbishopim3

CC: aran

Maniphest Tasks: T1536

Differential Revision: https://secure.phabricator.com/D6218