Add a missing test helper function

Signed-off-by: Ping Xie <pingxie@google.com>

tests/support/cluster_util.tcl

@@ -66,6 +66,21 @@ proc continuous_slot_allocation {masters} {
     }
 }
 
+# Assuming nodes are reset, this function performs slots allocation.
+# # Only the first 'masters' nodes are used.
+proc cluster_allocate_slots {masters replicas} {
+    set slot 16383
+    while {$slot >= 0} {
+        # Allocate successive slots to random nodes.
+        set node [randomInt $masters]
+        lappend slots_$node $slot
+        incr slot -1
+    }
+    for {set j 0} {$j < $masters} {incr j} {
+        R $j cluster addslots {*}[set slots_${j}]
+    }
+}
+
 # Setup method to be executed to configure the cluster before the
 # tests run.
 proc cluster_setup {masters node_count slot_allocator code} {