Steps to reproduce:

1. Deploy t1-lag topology to testbed;
2. Deploy t1-lag minigraph to DUT;
3. Wait for PortChannel interfaces to come up;
4. Bug -> When DUT and VMs exchange routes, some PortChannel interfaces tend to go down.

Version: SONiC-OS-HEAD.344-1be1c46

@lguohan @pavel-shirshov Did you observe similar problems on t1-lag? I am wondering if it is due to perforamance of our server.