Modify GET request handler for /oic/sec/acl

Modify GET request handler for /oic/sec/acl

Issue: If 'subject' field is not included in REST request,
       a error occur on HandleACLGetRequest.
       This implementation does not meet the spec, and causes the failure with CTT.

Resolution: A server responds for GET 'oic/sec/acl', even if 'subject' field
            is not included in REST request.

Patch 1: Fixed this issue, and adding GetACL API for debugging only.
Patch 2: Rebase it on the latest master branch

Change-Id: Icb3869fee6039a076ee90146ae94eb527a88865c
Signed-off-by: js126.lee <js126.lee@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/8633
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Chul Lee <chuls.lee@samsung.com>
Reviewed-by: Randeep Singh <randeep.s@samsung.com>