Make DrydockLog policy-aware

Summary: Ref T2015. Update DrydockLog for policy awareness and give it a policy query.

Test Plan: Browsed all the log interfaces.

Reviewers: btrahan

Reviewed By: btrahan

CC: hach-que, aran

Maniphest Tasks: T2015

Differential Revision: https://secure.phabricator.com/D7831