The circular dependency refactor will require deleting all of the
pipeline states as well as the event queues from ZK while zuul
is offline during the upgrade. This is fairly close to the existing
"delete-state" command, except that we can keep the config cache.
Doing so will allow for a faster recovery since we won't need to
issue all of the cat jobs again in order to fetch file contents.
To facilitate this, we add a "--keep-config-cache" argument to
the "delete-state" command which will then remove everything under
/zuul except /zuul/config.
Also, speed up both operations by implementing a fast recursive
delete method which sends async delete ops depth first and only
checks their results at the end (as opposed to the standard kazoo
delete which checks each operation at once).
This is added without a release note since it's not widely useful
and the upcoming change which requires its use will have a release
note with usage instructions.
Change-Id: I4db43e00a73f5e5b796261ffe7236ed906e6b421
c531adacae