Kill put job

A scenario can occur where a node will never be flushed if the node is dirty once the KIO::put job is finished. This patch aims to partially alleviate this issue by killing put jobs if the following is true:

1. The cache is dirty.
2. The job is less than 85% complete.
3. The job has not been killed more than twice previously due to the above two conditions being true.

This patch also deletes an unused method KIOFuseVFS::virtualPath.