Remove old device registration on the new registration

[janantala]

If the LWM2M Client sends a “Register” operation to the LWM2M Server even though the LWM2M Server has registration information of the LWM2M Client, the LWM2M Server removes the existing registration information and performs the new “Register” operation. This situation happens when the LWM2M Client forgets the state of the LWM2M Server (e.g., factory reset).

http://dev_devtoolkit.openmobilealliance.org/IoT/LWM2M10/doc/TS/index.html#!Documents/register.htm