confusing traces around the gateway selector

## Describe the bug
According to the trace above, the `ListStorageProviders` method from the gateway should be calling to several `ListStorageSpaces`. The server-side part of those `ListStorageSpaces` are from `storage-users`, `storage-shares` and `ocm`, all of them serving the `ListStorageSpaces` call.
The problem is that the client-side of the `ListStorageSpaces` call seems wrongly reported. Specially, several of them comes from the activitylog service, which doesn't even use the `ListStorageSpaces` call anywhere.

This might be a problem with the reva's selector pool, in this particular case, the gateway selector.
We're basically storing and getting a selector from the pool. If we need to store a new selector, the selector comes with the trace provider used by the service registering the selector.

Note that the activitylog service doesn't call nor implement the `ListStorageSpaces` method, so there is no reason for that call to be "attached" to the activitylog service. It's likely other service (or the gateway) the one making the call.

## Steps to reproduce
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## Expected behavior
A clear and concise description of what you expected to happen.

## Actual behavior
A clear and concise description of what happened.

## Setup
Please describe how you started the server and provide a list of relevant environment variables or configuration files.

```console
OCIS_XXX=somevalue
OCIS_YYY=somevalue
PROXY_XXX=somevalue
```

## Additional context
Add any other context about the problem here.