Protect the deleteOld step of TDB2 compaction

[afs]

This builds on #2254. The deleteOld step of compaction would benefit from further projection.

See #2127 (comment) for a description of compaction steps in Jena 5.0.0 and points vulnerability of the deleteOld step not completing properly.

This is separate to the issue on MS Windows whereby deletion of storage directories does not happen until the JVM exits.

One obvious cause of failing to completely delete old storage areas is server exit. Filesystem conditions such as being unable to delete a file are likely permanent errors requiring some repair to be carried out. Delete should not run into lack of disk space issues.