[IOT-1454] Change the Preconfigured-PIN OxM related defines to prevent conflict with...

[IOT-1454] Change the Preconfigured-PIN OxM related defines to prevent conflict with DCAP method.

  - Preconfigured-PIN OxM constant changed to 0xFF00
  - According to changes Preconfig-PIN OxM constant,
    OxM Callback array can't use anymore.
    So, Callback pointers are moved into the OTMContext.

Change-Id: Iefaf9de29bdb98809506df3b2efae35024cae4de
Signed-off-by: Chul Lee <chuls.lee@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/13681
Reviewed-by: Kevin Kane <kkane@microsoft.com>
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Randeep Singh <randeep.s@samsung.com>