Added option to sync vm config via csync2

When save_config_on_stop AND sync_config_on_save is enabled the config gets synced with csync2 -x vm.conf to all nodes configured in csync2. This will make sure that wherever the VM starts it will inherit the config changes.

we need to check that 'csync2' is available when this option is set before calling it. Right now sync_config could fail and we'd not have a clue.

perhaps in the validate funciton.

if sync config
    check_binary csync2