bufferinjector: Configure injector type

Change-Id: I6a77b3a66964d8674c1614897bfd6552d880b7d5
bufferinjector: Add task to src pad

Change-Id: I887edd3792b5e67bc7b71b8d3c387df97a221332
bufferinjector: Calculate waiting time based on buffer duration

Change-Id: I94cdf05449a156b1763ca680318dc29c8b7e55ba
bufferinjector: Add flags GAP and DROPPABLE to injected buffer

Change-Id: Ic5cad6b9495ca8a0e5853cec52062622970ce88f