Fix for running /etc/rc.local on Fedora

With systemd rc.local lives in /etc/rc.d and is only run
if the rc-local service is enabled.

This change creates a /etc/rc.d/rc.local symlink, and modifies img-functions
prepare_first_boot to tolerate an initially missing /etc/rc.local.

Fixes bug #1179674

Change-Id: I7e6102b62224950c1de5d48205dc4feff60f9389
Merge "Fix for running /etc/rc.local on Fedora"