Arvados

Configured disk cache size does not respect configuration entry due to two bugs:

1. Configured value does not get propagated from the loaded config to the disk cache code
2. Percentage values (including the default 10%) are computed as x% of free space, instead of x% of total filesystem size as intended

Additionally, the DiskCache logging is not connected when initialized by keepclient, so even with SystemLogs.LogLevel: debug the existing debugf() logs do not appear. We should fix this too.