[IOT-1591] Add warning code as notification type

[IOT-1591] Add warning code as notification type

It is required to notification message with warning type.

Change-Id: I8ea23690382a0f32d084ce3ed9903971f2a4c390
Signed-off-by: cc <ch79.cho@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/14639
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Uze Choi <uzchoi@samsung.com>
(cherry picked from commit d2671aafa1c61b98b2e20fbef0d9c57957526d17)
Reviewed-on: https://gerrit.iotivity.org/gerrit/14989
Reviewed-by: JungYong KIM <jyong2.kim@samsung.com>
Reviewed-by: Phil Coval <philippe.coval@osg.samsung.com>