Added token length to direct stack responses.

Added token length to direct stack responses.

Token length is required because the stack at the client side looks at
the token field only if token length is non zero. Without the token,
client application will not receive responses.

Change-Id: If1f9e85473bd964651669640d2fe48c1821600d5
Signed-off-by: Mandeep Shetty <mandeep.shetty@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/682
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Sakthivel Samidurai <sakthivel.samidurai@intel.com>
Reviewed-by: Erich Keane <erich.keane@intel.com>