Camera: Don't enable shutterdown for count down timer

For count down timer case, capture process should take place after
timer expiry. Otherwise flash is getting turned ON immediately after
pressing shutter button and then again during capture.

Fix made by not allowing to do anything related to capture process
except turning timer ON.

Change-Id: I843c88ccc9c03235dc6a2a7638221c778bfc6551
CRs-Fixed: 623445