Buildstream local cache doesn't get cleanup automatically when the disk is full
## Summary
If the disk gets fill up, build will fail and the only solution is to `rm -r` the buildstream cache folder
## What is the expected correct behavior?
If the disk is full, buildstream should automatically cleanup, similar to what what happen when you set a quota
## Possible fixes
A possible solution would be (when we fix #733) to change the defaults from
```
quota: infinity
```
to
```
quota: 100%
```
* BuildStream version affected: 1.2.3
issue