ContentRepositoryImpl should not call File.deleteOnExit

ContentRepositoryImpl.removeContent calls File.deleteOnExit if it can't delete the content or parent dirs. This is very wrong:

1) The grandparent dir may have other children completed unrelated to the item being removed.
2) The content in question may have been restored before process exit. For example, a deployment is undeployed, and then a while later the same bits are uploaded again.
3) File.deleteOnExit is a small memory leak. This one's relatively minor.