packaging: engine-encrypt-passwd.sh as standalone script

If ENGINE_CONFIG_IGNORE is set do not read configuration, this is useful
within installation phase, in which we do not have config yet.

Change-Id: I7b748fc787d44b2e877412f3107719d607b7a4ae
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>