Set engine id from vconf value when default config is set

Set engine id from vconf value when default config is set

- Issue:
When default configuration is loaded, invalid engine id can be set.

- Solution:
Default configuration stores fixed engine id, so the engine id can be
not installed in the image. Thus, this patch changes the logic for
loading default configuration. Through this patch, vconf value is used
default engine id when default configuration is loaded.

Change-Id: Ifa37d1eceb5df126b69ac7455aea0dc0e12005fa
Signed-off-by: Suyeon Hwang <stom.hwang@samsung.com>