BLASTBufferQueue: Avoid duplicate calls to setDefaultBufferSize

Calling in to the consumer may acquire the BufferQueueCore mutex. We call
BLASTBufferQueue::update from the UI thread. And so we can accidentally
end up blocking the UI thread on allocateBuffers() during app start-up.

Bug: 152501005
Test: Flip BLAST. Play.
Change-Id: I89034211ed5725b5be6391cc2bac748c0acf1eb3