[initramfs-xenclient]: On firstboot relabel the boot partition in the initramfs.

The first stuff that's run after the pivot (where the selinux policy
is loaded) require that the boot partition be labeled properly. This
is init.root-ro etc.
[dom0-fstab]: Remove use of user_xattrs.

These have nothing to do with SELinux. Not sure why we put this here
in the first place.
[xenclient-dom0-initscripts]: Relabel remaining rw mounts in mountall.sh on firstboot.
[xenclient-dom0-tweaks]: Remvoe autorelabel script.

This script doesn't fit well into the "embedded" model of OpenXT.
The problem this script is intended to solve (relabeling file systems)
should only be done OpenXT at the time of the firstboot.
[initramfs-xenclient]: Drop 'user_xattr' mount option for the rootfs.

This has nothing to do with SELinux and AFAIK we don't require it
for any other reason.
[xenclient-dom0-tweaks]: Make SELinux file labeling more targeted in firstboot.sh

Now that the bulk relabeling of the persistent volumes is handled
closer to where they're mounted the firstboot script can be more
targeted. This should make the first boot path a bit faster and the
firstboot script a bit ore clean.
[xenclient-root-ro]: Relabel r/w mounts on firstboot for measured firstboot path.