Fix panic in lisafs
Fix panic in lisafs

When mount fails, `filesystem.Release()` attempts to dereference a nil
`filesystem.clientLisa`.

PiperOrigin-RevId: 482027422

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