allow kdm to create /root/.kde/ with correct label

When the kdm service is started, it wants to create the .kde directory
under /root/, but SELinux denies that action. When the /root/.kde
directory exists, the kdm service wants to create a symlink in it,
but SELinux denies that action too. The intended symlink should
point this way:
 * /root/.kde/cache-machine-<FQDN> --> /var/tmp/kdecache-root

SELinux policy should now label the newly created /root/.kde
directory correctly as config_home_t, which is consistent with
other definitions. Allow rule for creating a symlink is already
defined.

Resolves: bz#2275868

policy/modules/services/xserver.if

@@ -2422,6 +2422,7 @@ interface(`xserver_filetrans_admin_home_content',`
 
 	optional_policy(`
 		gnome_cache_filetrans($1, xdm_home_t, dir, "xdm")
+		userdom_admin_home_dir_filetrans($1, config_home_t, dir, ".kde")
 	')
 ')