dracut.spec: add nohostonly and norescue subpackages

we need rpm subpackages, to be able to pull them in the installation
transaction for the initial %posttrans initramfs image creation.
lsinitrd.sh: simplify check for boot loader spec dirs
51-dracut-rescue.install: create directory, if it does not exist
systemd: local-fs.target is now root-fs.target and initrd-fs.target

Also rename dracut.target to initrd.target

see also systemd commit 700e07f
http://cgit.freedesktop.org/systemd/systemd/commit/?id=700e07f