[IOT-2463] Fix CTT failure for Get /oic/sec/roles

[IOT-2463] Fix CTT failure for Get /oic/sec/roles

Currently the GET request to the /oic/sec/roles resource will fail
with a 400 Bad Request code if the client doesn't have a Public Key
(non-certificate auth) or if the Public Key doesn't match any roles
certificates.

However, that is incorrect since the GET request to the
/oic/sec/roles resource was correct, it just doesn't have any roles
associated with it.

Changed the /oic/sec/roles resource to return an empty "roles" array
if the client doesn't have a Public Key or if the Public Key doesn't
match any roles certificates. At minimum, the return should be:

{
  "roles": [ ],
  "rt": ["oic.r.roles"],
  "if": ["oic.if.baseline"]
}

Testcase: CT1.7.9.1 Verify Security Virtual Resources conform to OIC
Schema

Change-Id: Id71c233875a6ef9e251f2adccd48907e5dedb1a1
Signed-off-by: Ibrahim Esmat <iesmat@microsoft.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/21733
Reviewed-by: Kevin Kane <kkane@microsoft.com>
Reviewed-by: Alex Kelley <alexke@microsoft.com>
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Randeep Singh <randeep.s@samsung.com>