samples: net: lwm2m_client: Updated RD client event handler
samples: net: lwm2m_client: Updated RD client event handler

Added missed LWM2M_RD_CLIENT_EVENT_ENGINE_SUSPENDED event handler

Signed-off-by: Juha Heiskanen <da286ad296b3dcaa6fdad737a1ad7c3ff3e427db@nordicsemi.no>

galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr,finikorg/zephyr,galak/zephyr,zephyrproject-rtos/zephyr