hotplug: Fix xendomains lock path for RHEL-based systems

hotplug: Fix xendomains lock path for RHEL-based systems

Commit c996572 changed the LOCKFILE path from a check between two
hardcoded paths (/var/lock/subsys/ or /var/lock) to using the
XEN_LOCK_DIR variable designated at configure time.  Since
XEN_LOCK_DIR doesn't (and shouldn't) have the 'subsys' postfix, this
effectively moves all the lock files by default to /var/lock instead.

Unfortunately, this breaks xendomains on RedHat-based SYSV init
systems.  RedHat-based SYSV init systems try to only call "${SERVICE}
shutdown" on systems which actually have an actively running
component; and they use the existence of /var/lock/subsys/${SERVICE}
to determine which systems are running.

Changing XEN_LOCK_DIR to /var/lock/subsys is not suitable, as only
system services like xendomains should create lockfiles there; other
locks (such as the console locks) should be created in /var/lock
instead.

Instead, re-instate the check for the subsys/ subdirectory of the lock
directory in the xendomains script.

Signed-off-by: George Dunlap <george.dunlap@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Olaf Hering <olaf@aepfle.de>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>