xend: Expose persistent domain path in xend conf file

This patch exposes the persistent (aka managed) domain path in xend
configuration file.  This option is already supported in XendOptions
but is not annotated in the configuration file.

Signed-off-by: Jim Fehlig <jfehlig@novell.com>

tools/examples/xend-config.sxp

@@ -245,3 +245,7 @@
 
 # Rotation count of qemu-dm log file.
 #(qemu-dm-logrotate-count 10)
+
+# Path where persistent domain configuration is stored.
+# Default is /var/lib/xend/domains/
+#(xend-domains-path /var/lib/xend/domains)