[Subport] Fix issues on portsorch.cpp

1. [Subport] Keep vlan tag when add member port into portchannel of subport

When add member port into portchannel, if the portchannel has subport interface,
the port should keep the vlan tag.

2. Handle HostIntfsStripTag properly

removeBridgePort should check port.m_child_ports.empty() before HostIntfsStripTag(,SAI_HOSTIF_VLAN_TAG_STRIP).

3. fix ERR syslog while test_subport setup/teardown

fix 2:

config portchannel add PortChannel1
config interface ip add PortChannel1.40 100.40.40.40/24

config interface ip remove PortChannel1.40 100.40.40.40/24
config portchannel del PortChannel1

syslog:
Dec 27 15:01:38.336049 as5812-54x NOTICE swss#orchagent: :- removeRouterIntfs: Router interface is still referenced
Dec 27 15:01:38.337833 as5812-54x ERR swss#orchagent: :- meta_generic_validation_remove: object 0x2000000000a81 reference count is 1, can't remove
Dec 27 15:01:38.338038 as5812-54x ERR swss#orchagent: :- removeLag: Failed to remove LAG PortChannel1 lid:2000000000a81

root cause:
portchannel is still reference by subport

solution: PortsOrch::doLagTask, op == DEL_COMMAND

=====
fix 3:

syslog:
Dec 24 17:28:01.030970 as5812-54x ERR swss#orchagent: :- meta_sai_validate_oid: oid is set to null object id on SAI_OBJECT_TYPE_LAG_MEMBER
Dec 24 17:28:01.031218 as5812-54x ERR swss#orchagent: :- setCollectionOnLagMember: Failed to enable collection on LAG member Ethernet28

root cause:
PortsOrch::setCollectionOnLagMember/ setDistributionOnLagMember, check lag member id

orchagent/portsorch.cpp

@@ -4835,6 +4835,13 @@ void PortsOrch::doLagTask(Consumer &consumer)
                 continue;
             }
 
+            if (!lag.m_child_ports.empty())
+            {
+                SWSS_LOG_NOTICE("LAG %s still has subport child, can't be removed", lag.m_alias.c_str());
+                it++;
+                continue;
+            }
+
             if (removeLag(lag))
                 it = consumer.m_toSync.erase(it);
             else
@@ -5633,12 +5640,14 @@ bool PortsOrch::removeBridgePort(Port &port)
             return parseHandleSaiStatusFailure(handle_status);
         }
     }
-
-    if (!setHostIntfsStripTag(port, SAI_HOSTIF_VLAN_TAG_STRIP))
+    if (port.m_child_ports.empty())
     {
-        SWSS_LOG_ERROR("Failed to set %s for hostif of port %s",
-                hostif_vlan_tag[SAI_HOSTIF_VLAN_TAG_STRIP], port.m_alias.c_str());
-        return false;
+        if (!setHostIntfsStripTag(port, SAI_HOSTIF_VLAN_TAG_STRIP))
+        {
+            SWSS_LOG_ERROR("Failed to set %s for hostif of port %s",
+                    hostif_vlan_tag[SAI_HOSTIF_VLAN_TAG_STRIP], port.m_alias.c_str());
+            return false;
+        }
     }
 
     //Flush the FDB entires corresponding to the port
@@ -6496,7 +6505,7 @@ bool PortsOrch::addLagMember(Port &lag, Port &port, string member_status)
 
     m_portList[lag.m_alias] = lag;
 
-    if (lag.m_bridge_port_id > 0)
+    if ((lag.m_bridge_port_id > 0) || !lag.m_child_ports.empty())
     {
         if (!setHostIntfsStripTag(port, SAI_HOSTIF_VLAN_TAG_KEEP))
         {
@@ -6544,7 +6553,7 @@ bool PortsOrch::removeLagMember(Port &lag, Port &port)
     lag.m_members.erase(port.m_alias);
     m_portList[lag.m_alias] = lag;
 
-    if (lag.m_bridge_port_id > 0)
+    if ((lag.m_bridge_port_id > 0) || !lag.m_child_ports.empty())
     {
         if (!setHostIntfsStripTag(port, SAI_HOSTIF_VLAN_TAG_STRIP))
         {
@@ -6601,6 +6610,10 @@ bool PortsOrch::setCollectionOnLagMember(Port &lagMember, bool enableCollection)
 {
     /* Port must be LAG member */
     assert(lagMember.m_lag_member_id);
+    if (!lagMember.m_lag_member_id)
+    {
+        return false;
+    }
 
     sai_status_t status = SAI_STATUS_FAILURE;
     sai_attribute_t attr {};
@@ -6632,6 +6645,10 @@ bool PortsOrch::setDistributionOnLagMember(Port &lagMember, bool enableDistribut
 {
     /* Port must be LAG member */
     assert(lagMember.m_lag_member_id);
+    if (!lagMember.m_lag_member_id)
+    {
+        return false;
+    }
 
     sai_status_t status = SAI_STATUS_FAILURE;
     sai_attribute_t attr {};