initial tests for AOF (and small changes to server.tcl to support these)

tests/support/util.tcl

@@ -188,3 +188,11 @@ proc createComplexDataset {r ops} {
         }
     }
 }
+
+proc formatCommand {args} {
+    set cmd "*[llength $args]\r\n"
+    foreach a $args {
+        append cmd "$[string length $a]\r\n$a\r\n"
+    }
+    set _ $cmd
+}