DO NOT MERGE libstagefright: Fix crash in convertMetaDataToMessage

- The ABuffer used for the Message has a preset value of 1024, if
  flattening the meta data exceeds this value, a check fails hence
  the crash.
- This change creates a new ABuffer if the buffer size would exceed
  the buffer capacity.

Bug: 22771132

CRs-Fixed: 857850

(cherry picked from commit 4bce6368)

Change-Id: Ia0a963e9872f646791e75b710ff9e227a66af4f9