* Use LWM2M security object as DTLS keystore by default
* Mark endpoint as secure regardless if DTLS peer exists or not
* Somewhat less debug output by default
The currently available options are:
* none - No keystore registered.
* simple - Keystore using fixed PSK credentials.
* lwm2m - Keystore based on LWM2M security objects
If an application wants to provide its own keystore, it selects 'none'
and registers its own at startup.
