mesh: Fix common.h issue in onoff_level_lighting_vnd_app

-Mbed TLS requires common.h to build. The sample provides common.h
 in sample folder level but included the path to zephyr_interface.
 This commit changes the include to be sample-specific

Signed-off-by: Frank Audun Kvamtrø <frank.kvamtro@nordicsemi.no>