Followup 682b4d0b88: bring this.isSetup back

682b4d0b88 removed the only line of code in ve.ce.ProtectedNode
that set this.isSetup to true. Consequently, it was always false,
and onProtectedTeardown would always short-circuit, so no ProtectedNode
would ever get torn down, which resulted in the expected chaos
of JS errors from event handlers that were never unbound.

Change-Id: Icc1748fd5acab4d97e80c88c3336e9d42b70e7ad
Merge "Followup 682b4d0b88: bring this.isSetup back"