Camera: Remove app segment stream's locked buffer tracking

The app segment CpuConsumer's max locked buffer count is already
enforced by the buffer queue. No need to monitor the locked buffer count
separately.

In case we are exceeding the max locked buffer count, the lockBuffer()
call returns failure, so further app segment processing will be deferred.

Test: vendor testing
Bug: 173583542
Change-Id: I02522bcc695ee00ac4ee48df4cfd76ce35522cb9