PriorityBlockingQueue doesn't preserve order within equal elements.
This means elements with same priority will be returned in
arbitrary order, which we don't want to have - for example we want
tiles to render in the same order they were added to the queue.
Also there is no measurable or felt benefit that priority bring so
lets just drop PriorityBlockingQueue for LinkedBlockingQueue.

Change-Id: I6ffe0bf896f0e18e8b5ffc75a4001d8f40515a56