base-files: preinit: Fixed sourcing of diag.sh in /etc/preinit. This caused errors due to frequent use of /proc/cpuinfo to determine board name to pick led layout. Now diag.sh (which only defines set_state and any helper functions) is sourced by a proper preinit function during preinit_main, which is after /proc has been brought up, unlike in /etc/preinit

SVN-Revision: 27501