Fixed possible memory leak condition.

Fixed possible memory leak condition.

Provisioning API returns list of unprovisioned devices. If parameter for
list is not null it can cause memory leak, changed code from just warning
from API to error and corrected test case according to it

Change-Id: I7ffe7efe116add643c1b062f2396d3486d677273
Signed-off-by: Randeep Singh <randeep.s@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/1203
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Sachin Agrawal <sachin.agrawal@intel.com>