Since the executor only periodically updates its state we could end up
scheduling much more tasks than the executor ActiveTasksLimit. This will happen
in the case of many parallel tasks that can all start at the same time.
To avoid this also considere the executor tasks saved in etcd that represent
the real view of scheduled tasks.
* objectstorage: remove `types` package and move `ErrNotExist` in base package
* objectstorage: Implement .Is and add helper `IsErrNotExist` for `ErrNotExist`
* util: Rename `ErrNotFound` to `ErrNotExist`
* util: Add `IsErr*` helpers and use them in place of `errors.Is()`
* datamanager: add `ErrNoDataStatus` to report when there's not data status in ost
* runservice/common: remove `ErrNotExist` and use errors in util package
Reorganize ExecutorTask to better distinguish between the task Spec and
the Status.
Split the task Spec in a sub part called ExecutorTaskSpecData that contains
tasks data that don't have to be saved in etcd because it contains data that can
be very big and can be generated starting from the run and the runconfig.
Export clients and related packages.
The main rule is to not import internal packages from exported packages.
The gateway client and related types are totally decoupled from the gateway
service (not shared types between the client and the server).
Instead the configstore and the runservice client currently share many types
that are now exported (decoupling them will require that a lot of types must be
duplicated and the need of functions to convert between them, this will be done
in future when the APIs will be declared as stable).
Just a raw replace of "github.com/pkg/errors".
Next steps will improve errors (like remote errors, api errors, not exist errors
etc...) to leverage its functionalities
rename the previous posix storage to posixflat and make it currently not user
selectable (since I'm not sure it's really worth using it).
The new posix storage uses the filesystem without any escaping so it's not a
real flat namespace.
This isn't a real issue since also minio is not a flat namespace and we are so
forced to use it like a hierarchycal filesystem.
Logs and archives can be shared by multiple runs. So removing a run doesn't
imply that we could also remote the logs and archives since they could be
"referenced" by another run.
Store also the runids as specific objects along with the logs and archives so,
we'll remove them only when no runids objects exist.
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
