Codec2 Components: reset OutputBlockPool after use

Since SimpleC2Component is holding the reference of output BlockPool,
destroying output BlockPool and creating a new BlockPool does not work.

Reset the reference of output BlockPool after
use(reset()/stop()/release()).

Bug: 184049126
Test: atest CtsMediaTestCases:android.media.cts.AdaptivePlaybackTest
Change-Id: I75fe1555533d75aa0f742e59992ae033f4454160