Audit ast_json_pack() calls for needed UTF-8 checks.

Added needed UTF-8 checks before constructing json objects in various
files for strings obtained outside the system.  In this case string values
from a channel driver's peer and not from the user setting channel
variables.

* aoc.c: Fixed type mismatch in s_to_json() for time and granularity json
object construction.

ASTERISK-26466
Reported by: Richard Mudgett

Change-Id: Iac2d867fa598daba5c5dbc619b5464625a7f2096