- In script checks, ensure we're running `Exec` against the new running
allocation and not the earlier stopped one.
- In script checks, allow `Exec` calls to error due to lack of pty when
we use the exec to kill the task.
- In `utils.go/RegisterAllocs`, force query for allocations to wait on
wait index returned by registration call.
Also refactor Consul ServiceClient to take a struct instead of a massive
set of arguments. Meant updating a lot of code but it should be far
easier to extend in the future as you will only need to update a single
struct instead of every single call site.
Adds an e2e test for canary tags.
