R1:7332599e0326

Provide an IDS_COUNTER mechanism for ID assignment

Summary: See D3912 for discussion. InnoDB may reuse autoincrement IDs after restart; provide a way to avoid it.

Test Plan: Unit tests. Scheduled and executed tasks through `drydock lease --type host` and `phd debug taskmaster`.

Reviewers: vrana, btrahan

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D3914