[IOT-1446] Fix discovery failure issue

[IOT-1446] Fix discovery failure issue

Change logic in the Policy Engine in order to resolve
discovery failure issue

Patch #1: Initial upload
Patch #2: Error message changed

Change-Id: I08ab1dec15cb0f49374d42d97b65a23fe885db39
Signed-off-by: Jongmin Choi <jminl.choi@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/13173
Reviewed-by: Kevin Kane <kkane@microsoft.com>
Reviewed-by: Nathan Heldt-Sheller <nathan.heldt-sheller@intel.com>
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Randeep Singh <randeep.s@samsung.com>