HLS: remove no more than 10% of bandwidth history at a time

- fix a 'possible video time jump' after seek, don't update
  renderer anchor time for 0-sized audio buffers

- fix another 'possible video time jump' caused by some states
  not reset in mStreams

- bandwidth estimator changes to not remove more than 10%
  of total transfer duration at a time to avoid jumping up
  too quickly

bug: 20267388
related-to-bug: 19864613
related-to-bug: 20138395

Change-Id: I8812332cd1e26bf562acfaf086fd679a3549debc