When a lease triggers a resource allocation for a resource which must activate, awaken the lease task after the resource activates

Summary:
Depends on D19753. Ref T13210. This is a small optimization that saves us from waiting up to 15 seconds for a yield.

When there are no Working Copy resources and a new lease comes in, we'll allocate one and yield until it activates.

If activating it (SSH'ing and running `git clone`) takes less than 15 seconds, the resource will activate (say, at T+4) but the lease won't update again for a while (say, until T+15). This leaves us with a pointless wait (in this example, we're sitting around for 9 seconds when we could move forward).

To improve this a little bit, let resources wake up the lease update tasks that triggered allocation after they activate. In the best case, that task runs ~15 seconds sooner. In the worst case, the awaken is just a no-op.

With a more-full queue, this has a smaller effect (it's likely something else will run and be able to use the resource in those 9 seconds).

With already-activated resources, this has no effect (when resources are already activated, we can lease immediately).

Test Plan:
- Cleaned up all working copy resources.
- Requested a new "A" working copy.
- Before patch: got a working copy after 17-18 seconds, most of which was spent yielded.
- After patch: got a working copy after 3-4 seconds.

Reviewers: amckinley

Reviewed By: amckinley

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T13210

Differential Revision: https://secure.phabricator.com/D19754