Correct the ENUM value of OTM according to spec.

Correct the ENUM value of OTM according to spec.

- Issue : Compliance issue on OTM type
- Solution : Samsung suggest to revive enum type of OTM, and make URN type to optional and ENUM type to mandatory/
            THis patch is for this solution.
     oic:justwork = 0, oic:randompin = 1, oic:mfgcert = 2

Note : Need to apply this patch, once ENUM type of OTM is revived on Spec.

Change-Id: Id0ae1fcf4175576ff2afd7fde7e473942c391f66
Signed-off-by: js126.lee <js126.lee@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/3467
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Ashwini  Kumar <k.ashwini@samsung.com>
Reviewed-by: Woochul Shim <woochul.shim@samsung.com>
Reviewed-by: Dmitriy Zhuravlev <d.zhuravlev@samsung.com>
Reviewed-by: Sachin Agrawal <sachin.agrawal@intel.com>