Prevent reading past the end of the buffer in 3GPP

Metadata processed within the parse3GPPMetaData function may not be NUL
terminated and thus calling setCString may read out of bounds. Ensure
proper NUL termination, but take care not to interfere with other special
cases (ie, albm).

Bug: 20923261
Change-Id: Ie93b3038b534b4c4460571a68f4d734cff7ad324
(cherry picked from commit 5cea0155)