Expected behavior:
When a shrieker is triggered, an observer watching it will emit 1 pulse when it starts shrieking, and 1 pulse when it stops – because this is a block state change. Parity with Java and consistent observer behavior.

Observed behavior:
Observer does not emit a pulse when entering the shrieking block state, and will pulse once when exiting the shrieking block state. This is not in parity with java and is inconsistent with other observer behavior.

Steps to reproduce:
1. Place down 1 shrieker
2. Face an observer so it watches the shrieker
3. Place a redstone lamp next to the observer, to count the pulses
4. Stand on top of the shrieker, allowing it to enter the shrieking state, and then leave it. 
5. Watch the shrieker pulse only when shrieking stops.