Added missing AUTHENTICATION_FAILED OCException reason.

Added missing AUTHENTICATION_FAILED OCException reason.

Fixed warning about missing OC_STACK_AUTHENTICATION_FAILED case in
OCException::reason() switch statement, and added appropriate
corresponding string constant.

Change-Id: Ibdc2d68f9cfb76f8165a62bce65dc183b19d7622
Signed-off-by: Ossama Othman <ossama.othman@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/4709
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Chul Lee <chuls.lee@samsung.com>
Reviewed-by: Ivan Pazderskyy <i.pazderskyy@samsung.com>
Reviewed-by: Andrii Shtompel <a.shtompel@samsung.com>
Reviewed-by: Dmitriy Zhuravlev <d.zhuravlev@samsung.com>