Create parent directory in merge_config_file

The code accounts for the config file not existing but it does not
account for the parent directory missing. This is currently breaking any
Ironic jobs that disable Nova.

Change-Id: Ia5fcfe6c63f5cc40b11f7e1f3be244d7897f26f6

Author: dtantsur

inc/meta-config

@@ -90,6 +90,7 @@ function merge_config_file {
     local real_configfile
     real_configfile=$(eval echo $configfile)
     if [ ! -f $real_configfile ]; then
+        mkdir -p $(dirname $real_configfile) || die $LINENO "could not create the directory of $real_configfile ($configfile)"
         touch $real_configfile || die $LINENO "could not create config file $real_configfile ($configfile)"
     fi