use /run instead of /dev/.run

use /run instead of /dev/.run

Instead of the /dev/.run trick we have currently implemented, we decided
to move the early-boot runtime dir to /run.

An existing /var/run directory is bind-mounted to /run. If /var/run is
already a symlink, no action is taken.

An existing /var/lock directory is bind-mounted to /run/lock.
If /var/lock is already a symlink, no action is taken.

To implement the directory vs. symlink logic, we have a:
  ConditionPathIsDirectory=
now, which is used in the mount units.

Skipped mount unit in case of symlink:
  $ systemctl status var-run.mount
  var-run.mount - Runtime Directory
    Loaded: loaded (/lib/systemd/system/var-run.mount)
    Active: inactive (dead)
            start condition failed at Fri, 25 Mar 2011 04:51:41 +0100; 6min ago
     Where: /var/run
      What: /run
    CGroup: name=systemd:/system/var-run.mount

The systemd rpm needs to make sure to add something like:
  %pre
  mkdir -p -m0755 /run >/dev/null 2>&1 || :
or it needs to be added to filesystem.rpm.

Udev -git already uses /run if that exists, and is writable at bootup.
Otherwise it falls back to the current /dev/.udev.

Dracut and plymouth need to be adopted to switch from /dev/.run to run
too.

Cheers,
Kay