Add packet-drop to fix the new flaky failover test (valkey-io#2196)

The new test was added in valkey-io#2178, obviously there may be
pending reads in the connection, so there may be a race
in the DROP-CLUSTER-PACKET-FILTER part causing the test
to fail. Add CLOSE-CLUSTER-LINK-ON-PACKET-DROP to ensure
that the replica does not process the packet.

Signed-off-by: Binbin <[email protected]>

Author: enjoy-binbin

tests/unit/cluster/failover2.tcl

@@ -147,6 +147,7 @@ proc test_replica_config_epoch_failover {type} {
             R 3 CONFIG SET cluster-replica-no-failover yes
         }
         R 3 DEBUG DROP-CLUSTER-PACKET-FILTER $CLUSTER_PACKET_TYPE_ALL
+        R 3 DEBUG CLOSE-CLUSTER-LINK-ON-PACKET-DROP 1
 
         set R0_nodeid [R 0 cluster myid]
 
@@ -169,6 +170,7 @@ proc test_replica_config_epoch_failover {type} {
         # Pause the R 0 and wait for the cluster to be down.
         pause_process [srv 0 pid]
         R 3 DEBUG DROP-CLUSTER-PACKET-FILTER $CLUSTER_PACKET_TYPE_NONE
+        R 3 DEBUG CLOSE-CLUSTER-LINK-ON-PACKET-DROP 0
         wait_for_condition 1000 50 {
             [CI 1 cluster_state] == "fail" &&
             [CI 2 cluster_state] == "fail" &&