Remove unnecessary setter/getter related errorcode for response

Remove unnecessary setter/getter related errorcode for response

There are invalid APIs setErrorCode/getErrorCode in C++ layer.
It can be caused a big confusion to user.
Since the value never transfer on network. it just set in class inside.
Thur, It is better to remove the methods.

Change-Id: Iab863b1c16095ec77b9733bd3ff0ea38167b2dba
Signed-off-by: jihwan.seo <jihwan.seo@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/13151
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Dave Thaler <dthaler@microsoft.com>
Reviewed-by: Jaewook Jung <jw0213.jung@samsung.com>
Reviewed-by: JungYong KIM <jyong2.kim@samsung.com>
Reviewed-by: Ashok Babu Channa <ashok.channa@samsung.com>
Reviewed-by: Ziran Sun <ziran.sun@samsung.com>
Reviewed-by: Jaehong Jo <jaehong.jo@samsung.com>
Reviewed-by: Rick Bell <richard.s.bell@intel.com>
Reviewed-by: Uze Choi <uzchoi@samsung.com>