Fix bug for multiple extras of message.

Fix bug for multiple extras of message.

When the receive multiple extras in the message from notification provider,
consuemr service misparse as parsing just one extras for incorrect operation of pointers.
In this patch, incorrect operation of pointers is fixed.

Change-Id: Ifacaf247ca836d81031ffe93b0b72d2b46db65f3
Signed-off-by: KIM JungYong <jyong2.kim@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/12745
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Uze Choi <uzchoi@samsung.com>