Fix key generation in removeDecapTunnel (#2322)

*After the latest changes in this PR #2190 an issue was introduced. When the tunnel was deleted the TunnelTermEntries were deleted from ASIC but not from the OA cache. Due to that then the same tunnel is created the TunnelTermEntries are not created as OA has it in local cache.
Signed-off-by: Myron Sosyak <myronx.sosyak@intel.com>

orchagent/tunneldecaporch.cpp

@@ -67,7 +67,7 @@ void TunnelDecapOrch::doTask(Consumer& consumer)
         {
             tunnel_id = tunnelTable[key].tunnel_id;
         }
-        
+
         if (op == SET_COMMAND)
         {
 
@@ -240,11 +240,11 @@ void TunnelDecapOrch::doTask(Consumer& consumer)
                 ++it;
                 continue;
             }
-            
+
             //create new tunnel if it doesn't exists already
             if (valid && !exists)
             {
-                
+
                 if (addDecapTunnel(key, tunnel_type, ip_addresses, p_src_ip, dscp_mode, ecn_mode, encap_ecn_mode, ttl_mode,
                                     dscp_to_tc_map_id, tc_to_pg_map_id))
                 {
@@ -427,7 +427,7 @@ bool TunnelDecapOrch::addDecapTunnel(
         attr.value.oid = tc_to_pg_map_id;
         tunnel_attrs.push_back(attr);
     }
-    
+
     // write attributes to ASIC_DB
     sai_object_id_t tunnel_id;
     status = sai_tunnel_api->create_tunnel(&tunnel_id, gSwitchId, (uint32_t)tunnel_attrs.size(), tunnel_attrs.data());
@@ -669,8 +669,8 @@ bool TunnelDecapOrch::setTunnelAttribute(string field, sai_object_id_t value, sa
     {
         // TC remapping.
         attr.id = SAI_TUNNEL_ATTR_DECAP_QOS_DSCP_TO_TC_MAP;
-        attr.value.oid = value; 
-        
+        attr.value.oid = value;
+
     }
     else if (field == decap_tc_to_pg_field_name)
     {
@@ -763,7 +763,16 @@ bool TunnelDecapOrch::removeDecapTunnel(string table_name, string key)
     for (auto it = tunnel_info->tunnel_term_info.begin(); it != tunnel_info->tunnel_term_info.end(); ++it)
     {
         TunnelTermEntry tunnel_entry_info = *it;
-        string term_key = tunnel_entry_info.src_ip + '-' + tunnel_entry_info.dst_ip;
+        string term_key;
+        swss::IpAddress src_ip(tunnel_entry_info.src_ip);
+        if (!src_ip.isZero())
+        {
+            term_key = src_ip.to_string() + '-' + tunnel_entry_info.dst_ip;
+        }
+        else
+        {
+            term_key = tunnel_entry_info.dst_ip;
+        }
         if (!removeDecapTunnelTermEntry(tunnel_entry_info.tunnel_term_id, term_key))
         {
             return false;