Prevent empty credential to be added

Prevent empty credential to be added

Prevent empty credential to be added
(e.g. only rowneruuid is sent)

Patch #1: initial upload
Patch #2-3: fix arduino build error

Change-Id: I7802dcb76daab3269eb0a9638659087643b0c141
Signed-off-by: Jongmin Choi <jminl.choi@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/13379
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Randeep Singh <randeep.s@samsung.com>
(cherry picked from commit 9366b7f721f6fe0c526832baf26b102984c7dcee)
Reviewed-on: https://gerrit.iotivity.org/gerrit/13445