Implement runservice maintenance mode and export/import.
When runservice is set in maintenance mode it'll start only the maintenance and
export/import handlers.
Setting maintenance mode will set a key in etcd so all the runservice instances
will detect it and enter in maintenance mode. This is done asyncronously so it
could take some time (future improvements will add some api to show all the
runservice states)
Export is always available and will export the datamanager contents. Currently
only datamanager contents are exported (no logs and workspace archives).
Import is available only during maintenance, given a datamanager export will
import it and reset etcd to this import state.
* Don't make cors enabled on all (*) by default.
* Handle related web.allowedOrigins options
* Only the gateway api should be called by a browser so setup the cors handler
only on it
Don't put datamanager base dirs inside the root of the ost but use a base path.
Let's do it now before releasing since this is a breaking change that requires
moving the ost data to the new path
Also if they are logically part of the runservice the names runserviceExecutor
and runserviceScheduler are long and quite confusing for an external user
Simplify them separating both the code parts and updating the names:
runserviceScheduler -> runservice
runserviceExecutor -> executor
Simone Gotti