hammer2 - major simplification 1/many (stabilization)
* Fix a dirty chain leak due to detached inodes and the delayed vnode
deactivation that DragonFly does. A cache_unlink() call was missing
to properly cycle the vnode in the nrename path and a
hammer2_cluster_delete() needed the DELETE_PERMANENT flag to handle the
case where the vnode was already detached.
* Fix an inode reference count leak, callers of hammer2_inode_common_parent()
were not properly dropping the returned inode.
* Fix a deadlock due to front-end vs write-thread interactions. nvtruncbuf()
calls must not be made with an inode lock held.
* Cleanup some debugging, add some debugging.