Fix flakiness in TestDisruptions for two pc testing (#17106)

Signed-off-by: Manan Gupta <manan@planetscale.com>

Author: GuptaManan100

go/test/endtoend/cluster/vtctldclient_process.go

@@ -195,7 +195,9 @@ func (vtctldclient *VtctldClientProcess) PlannedReparentShard(Keyspace string, S
 	output, err := vtctldclient.ExecuteCommandWithOutput(
 		"PlannedReparentShard",
 		fmt.Sprintf("%s/%s", Keyspace, Shard),
-		"--new-primary", alias)
+		"--new-primary", alias,
+		"--wait-replicas-timeout", "30s",
+	)
 	if err != nil {
 		log.Errorf("error in PlannedReparentShard output %s, err %s", output, err.Error())
 	}

go/test/endtoend/transaction/twopc/utils/utils.go

@@ -221,6 +221,10 @@ func AddShards(t *testing.T, clusterInstance *cluster.LocalProcessCluster, keysp
 		shard, err := clusterInstance.AddShard(keyspaceName, shardName, 3, false, nil)
 		require.NoError(t, err)
 		clusterInstance.Keyspaces[0].Shards = append(clusterInstance.Keyspaces[0].Shards, *shard)
+		for _, vttablet := range shard.Vttablets {
+			err = vttablet.VttabletProcess.WaitForTabletStatuses([]string{"SERVING"})
+			require.NoError(t, err)
+		}
 	}
 }