openshift.ks: CONF_ABORT_ON_UNRECOGNIZED_SETTINGS

Add the `abort_on_unrecognized_settings`/`CONF_ABORT_ON_UNRECOGNIZED_SETTINGS` setting, which defaults to true and causes the installation script to abort if an unrecognized setting is specified if enabled or causes the installation script only to warn about unrecognized settings if disabled.
    
Make `parse_kernel_cmdline` set an overriding default value of `CONF_ABORT_ON_UNRECOGNIZED_SETTINGS=false` so that kickstart scripts do not abort because of kernel command-line arguments that are unrelated to the installation script.
    
This commit fixes bug 1114519.