rcctl.8: Add missing variable

[Matthew Martin]

diff --git rcctl.8 rcctl.8
index 6c3048b834c..93a76a937c1 100644
--- rcctl.8
+++ rcctl.8
@@ -64,6 +64,7 @@ can be one of
 .Cm class ,
 .Cm flags ,
 .Cm logger ,
+.Cm rtable ,
 .Cm status ,
 .Cm timeout
 or