create-user-key-store.sh: replace weak des3 encryption with aes256
create-user-key-store.sh: replace weak des3 encryption with aes256

Replace weak des3 encryption with more secure algorithm aes256 to
generate ima key in script create-user-key-store.sh.

Signed-off-by: David Dunlap <5dc5ac643f5e1f771aecbe7c43e31e482a710328@windriver.com>
Signed-off-by: Kai Kang <12cd79c4a5e843cb1f0f6ae2d45a5336990c82a6@windriver.com>

jiazhang0/meta-secure-core,jiazhang0/meta-secure-core,jiazhang0/meta-secure-core,jiazhang0/meta-secure-core