Revert "ext4: optimize test_root()"

This reverts commit 5b2b9dae7a3fa5475d71567efa4d9b854e46c625.
Revert "ext4: speed up truncate/unlink by not using bforget() unless needed"

This reverts commit 2148fda90aba637100331fadbf2e8f234cb4e1c3.