Fix VFS2 gofer open(O_CREAT) reference leak.
Fix VFS2 gofer open(O_CREAT) reference leak.

gofer.filesystem.createAndOpenChildLocked() doesn't need to take a reference on
the new dentry since vfs.FileDescription.Init() will do so.

PiperOrigin-RevId: 314242127

google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor