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 9c170c07)

Change-Id: I056ade2f95bc8d82dfe092de7ecddba588cc5b72