prevent remote deletion after local deletion due to fileObserver

Description

Without the MR, when a file is removed on the cloud, then eDrive remove it on device. This triggered the FileEventListener (which detect deletion on device) which ask for a remote deletion request.

Same happened after a download, an Upload request where tried to send (but not executed in this particular case).

With this MR, neither the upload, neither the remote deletion request are sent anymore.

Technical details

Also prevent an NPE in SynchronizationService.OnRemoteOperationFinish()

Tests

• Delete a synced file from the cloud
• Download a file from the cloud
• Upload a new file

Issues

https://gitlab.e.foundation/e/os/backlog/-/issues/921

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