Make various Drydock improvements

Summary:
Tightens up a bunch of stuff:

• In drydock lease, pull and print logs so the user can see what's happening.
• Remove DrydockAllocator, which was a dumb class that did nothing. Move the tiny amount of logic it held directly to DrydockLease.
• Move resourceType from worker task metadata directly to DrydockLease. Other things (like the web UI) can be more informative with this information available.
• Pass leases to allocateResource(). We always allocate in response to a lease activation request, and the lease often has vital information. This also allows us to associate logs with leases correctly.

Test Plan: Ran drydock lease --type host and saw it perform a host allocation in EC2.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2015

Differential Revision: https://secure.phabricator.com/D3870