[RouteOrch] Orchagent crashed when add and delete route at same time.

[yangyue8]

Description
The refcount of nexthop is incorrect when delete and add route at the same time, which causes orchagent crashed.

Error Log

2024-11-25.06:00:49.527708|R|SAI_OBJECT_TYPE_ROUTE_ENTRY||
{"dest":"100.1.40.0/24","switch_id":"oid:0x21000000000000","vr":"oid:0x3000000000477"}
2024-11-25.06:00:49.530093|C|SAI_OBJECT_TYPE_ROUTE_ENTRY||
{"dest":"100.1.40.0/24","switch_id":"oid:0x21000000000000","vr":"oid:0x3000000000478"}
|SAI_ROUTE_ENTRY_ATTR_NEXT_HOP_ID=oid:0x4000000000491
2024-11-25.06:00:49.532539|a|SYNCD_INVOKE_DUMP

2024 Nov 25 06:00:49.532717 sonic ERR swss#orchagent: :- removeMplsNextHop: Failed to remove next hop push17/148+100.1.48.1@Ethernet1, rv:-17
2024 Nov 25 06:00:49.532717 sonic ERR swss#orchagent: :- handleSaiRemoveStatus: Encountered failure in remove operation, exiting orchagent, SAI API: SAI_API_NEXT_HOP, status: SAI_STATUS_OBJECT_IN_USE
2024 Nov 25 06:00:49.532753 sonic NOTICE swss#orchagent: :- notifySyncd: sending syncd: SYNCD_INVOKE_DUMP