[ssw] clean up DPU_APPL_DB and DPU_STATE_DB for DPU swss restart or DPU reboot (#25578)

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reference: https://github.com/sonic-net/sonic-buildimage/blob/master/src/sonic-yang-models/yang-models/sonic-device_metadata.yang#L197

#### Why I did it
For sonic-net/SONiC#2175

sign-off: Jing Zhang [email protected]

##### Work item tracking
- Microsoft ADO **(number only)**:

#### How I did it
1. Check if DPU_APPL_DB is pingable
2. If yes, flush all DB entries when swss starts.

#### How to verify it
Tested on ssw testbed.
- Entries got removed.
```
$ redis-cli -p 6381 -n 15
127.0.0.1:6381[15]> keys *
1) "BFD_SESSION_TABLE:default:default:10.1.0.32"
2) "BFD_SESSION_TABLE:default:default:10.1.2.32"
3) "BFD_SESSION_TABLE:default:default:10.1.1.32"
127.0.0.1:6381[15]> keys *
(empty array)
```

```
$ redis-cli -p 6381 MONITOR
OK

... ...
1769395816.952661 [18 169.254.200.1:34286] "PING"
1769395816.952718 [16 169.254.200.1:34280] "PING"
1769395816.954712 [17 169.254.200.1:34296] "SELECT" "17"
1769395816.954877 [17 169.254.200.1:34296] "PING"
1769395817.183169 [15 169.254.200.1:34310] "SELECT" "15"
1769395817.183386 [15 169.254.200.1:34310] "PING"
1769395817.210425 [15 169.254.200.1:34320] "SELECT" "15"
1769395817.210602 [15 169.254.200.1:34320] "FLUSHDB"
1769395817.229074 [17 169.254.200.1:34322] "SELECT" "17"
1769395817.229309 [17 169.254.200.1:34322] "FLUSHDB"
```
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#### Link to config_db schema for YANG module changes
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Author: mssonicbld

files/scripts/swss.sh

@@ -408,6 +408,20 @@ start() {
         $SONIC_DB_CLI RESTAPI_DB FLUSHDB
         clean_up_tables STATE_DB "'PORT_TABLE*', 'MGMT_PORT_TABLE*', 'VLAN_TABLE*', 'VLAN_MEMBER_TABLE*', 'LAG_TABLE*', 'LAG_MEMBER_TABLE*', 'INTERFACE_TABLE*', 'MIRROR_SESSION*', 'VRF_TABLE*', 'FDB_TABLE*', 'FG_ROUTE_TABLE*', 'BUFFER_POOL*', 'BUFFER_PROFILE*', 'MUX_CABLE_TABLE*', 'ADVERTISE_NETWORK_TABLE*', 'VXLAN_TUNNEL_TABLE*', 'VNET_ROUTE*', 'MACSEC_PORT_TABLE*', 'MACSEC_INGRESS_SA_TABLE*', 'MACSEC_EGRESS_SA_TABLE*', 'MACSEC_INGRESS_SC_TABLE*', 'MACSEC_EGRESS_SC_TABLE*', 'VRF_OBJECT_TABLE*', 'VNET_MONITOR_TABLE*', 'BFD_SESSION_TABLE*', 'SYSTEM_NEIGH_TABLE*', 'FABRIC_PORT_TABLE*', 'TUNNEL_DECAP_TABLE*', 'TUNNEL_DECAP_TERM_TABLE*'"
         $SONIC_DB_CLI APPL_STATE_DB FLUSHDB
+        # Flush DPU remote databases (DPU device only)
+        # Only run if this is a DPU device (type=SmartSwitchDPU or switch_type=dpu)
+        DEVICE_TYPE=`$SONIC_DB_CLI CONFIG_DB hget "DEVICE_METADATA|localhost" type`
+        SWITCH_TYPE=`$SONIC_DB_CLI CONFIG_DB hget "DEVICE_METADATA|localhost" switch_type`
+        if [[ x"${DEVICE_TYPE}" == x"SmartSwitchDPU" || x"${SWITCH_TYPE}" == x"dpu" ]]; then
+            # Check if DPU_APPL_DB remote database is reachable
+            if $SONIC_DB_CLI DPU_APPL_DB PING >/dev/null 2>&1; then
+                debug "Flushing DPU remote databases (DPU_APPL_DB, DPU_STATE_DB, DPU_APPL_STATE_DB, DPU_COUNTERS_DB) ..."
+                $SONIC_DB_CLI DPU_APPL_DB FLUSHDB
+                $SONIC_DB_CLI DPU_STATE_DB FLUSHDB
+                $SONIC_DB_CLI DPU_APPL_STATE_DB FLUSHDB
+                $SONIC_DB_CLI DPU_COUNTERS_DB FLUSHDB
+            fi
+        fi
         clean_up_chassis_db_tables
         rm -rf /tmp/cache
         MEDIA_SETTINGS="/usr/share/sonic/device/$PLATFORM/media_settings.json"