messages: use printf to get escape character

Also, don't use colors unless we have a terminal.
initrd: also copy insmod if not in busybox
initrd: handle the case we are installed in a directory with spaces
qemu: don't use `-no-user-config`

This option is already present in `-nodefconfig`
qemu: don't export root FS as read-only

With older versions of qemu, it seems that this prevents more than what
we would expect. execve() would return EROFS...
initrd: be quiet when testing insmod