SDK file delete fails to delete_all with delete_from_download_dir in some cases

Nobody has claimed this yet.

## The Issue

In order to delete files efficiently,
as a sdk user,
I want --delete_all and --delete_from_download_dir to work at the same time.

### Steps to reproduce
1. Download more than one video from the same channel
2. /opt/lbry/lbrynet file delete --channel_name=@ChannelName --delete_all --delete_from_download_dir

3. Look to see if the files are still in the directory.

### Expected behaviour
Expected to have my HD space back.

### Actual behaviour
Files still there.

## System Configuration

```
{
"build": "release",
"desktop": "Unknown",
"distro": {
"codename": "xenial",
"id": "ubuntu",
"like": "debian",
"version": "16.04",
"version_parts": {
"build_number": "",
"major": "16",
"minor": "04"
}
},
"lbrynet_version": "0.32.3",
"lbryschema_version": "0.0.16",
"os_release": "4.4.0-1075-aws",
"os_system": "Linux",
"platform": "Linux-4.4.0-1075-aws-x86_64-with-debian-stretch-sid",
"processor": "x86_64",
"python_version": "3.7.1"
}
```

## Internal Use

### Acceptance Criteria
1.
2.
3.

### Definition of Done
- [ ] Tested against acceptance criteria
- [ ] Tested against the assumptions of user story
- [ ] The project builds without errors
- [ ] Unit tests are written and passing
- [ ] Tests on devices/browsers listed in the issue have passed
- [ ] QA performed & issues resolved
- [ ] Refactoring completed
- [ ] Any configuration or build changes documented
- [ ] Documentation updated
- [ ] Peer Code Review performed

Start by reproducing the issue with the documented `lbrynet file delete` command using `--channel_name`, `--delete_all`, and `--delete_from_download_dir` after downloading multiple videos from one channel. Trace the file-delete command entry point and its handling of both flags; done means the matching files are removed from the download directory and unit tests pass.

Written by the indexing model from the issue text.