Revertq "update public certificate and enable certificate verification"

This reverts commit 477ebb95900706655957ae445c46864514c69883.

Signed-off-by: Dongjin Kim <tobetter@gmail.com>

Conflicts:
	samples/c/Makefile
Fix serivce corruption due memory conflict.

Signed-off-by: Dongjin Kim <tobetter@gmail.com>