amstream: fix crash when update ext stbuf metainfo. [1/1]

amstream: fix crash when update ext stbuf metainfo. [1/1]

PD#SWPL-33180

Problem:
1. fix crash when update ext stbuf metainfo.
2. delay put fd cause playback stuck.

Solution:
1. add some null check for metainfo update.
2. If it is the single instance that the pipeline of DTV used,
   then have to check that the resources which is work on the
   tunnel are being released.

Verify:
ah212

Change-Id: Iaa68a6c2b4fcd0b8dbea30603c2d6e4e3463160e
Signed-off-by: shihong.zheng <shihong.zheng@amlogic.com>