Fix CI flaky tests (#14531)

- https://github.com/redis/redis/actions/runs/19200504999/job/54887625884
   avoid calling `start_write_load` before pausing the destination node

- https://github.com/redis/redis/actions/runs/18958533020/job/54140746904
maybe the replica did not sync with master, then the replica did not update the counter

tests/unit/cluster/atomic-slot-migration.tcl

@@ -1342,12 +1342,9 @@ start_cluster 3 3 {tags {external:skip cluster} overrides {cluster-node-timeout
         # start migration from #0 to #1
         set task_id [setup_slot_migration_with_delay 0 1 0 100]
 
-        # Create some traffic on slot 0, so the destination node will enter streaming buffer state
+        # Create 200 keys of 16k size traffic on slot 0, streaming buffer need 10s (200*50ms)
         populate_slot 200 -idx 0 -slot 0 -size 16384
 
-        # Start the slot 0 write load on the R 0
-        set load_handle [start_write_load "127.0.0.1" [get_port 0] 100 [slot_key 0 mykey] 500]
-
         # wait for streaming buffer state, then pause the destination node
         wait_for_condition 1000 20 {
             [string match {*streaming-buffer*} [migration_status 1 $task_id state]]
@@ -1356,6 +1353,9 @@ start_cluster 3 3 {tags {external:skip cluster} overrides {cluster-node-timeout
         }
         pause_process $r1_pid
 
+        # Start the slot 0 write load on the R 0
+        set load_handle [start_write_load "127.0.0.1" [get_port 0] 100 [slot_key 0 mykey] 500]
+
         # the source node will fail after several seconds (including the time
         # to fill the socket buffer of source node), the main channel can not
         # write data to destination since the destination is paused

tests/unit/moduleapi/cluster.tcl

@@ -177,6 +177,7 @@ start_cluster 2 2 [list tags {external:skip cluster modules} config_lines $modul
         $master2 set count_dels_{4oi} 1
         $master2 del count_dels_{4oi}
         assert_equal 1 [$master2 keyspace.get_dels]
+        wait_for_ofs_sync $master2 $replica2
         assert_equal 1 [$replica2 keyspace.get_dels]
         $master2 set count_dels_{4oi} 1