Add a test that catches this.

Simplifies the API, and fixes a race condition.

happen to know a lot of inodes.

PathNodeFs.{addChild,rmChild} now calls Inode.{AddChild,RmChild}
rather than the reverse, and PathNodeFs manages its own locking.

Remove methods:

- FileSystemConnector.renameUpdate
- FileSystemConnector.unlinkUpdate
- FileSystemConnector.createChild
- Inode.CreateChild
- Inode.LockTree

Instead, add File.SetInode(), so Files can update inodes if needed.

This prevents forgetting or overwriting the Ino field.  Add a test.

- LoggingFileSystem
- PathDebugFileSystem
- TimingFileSystem

needed.