no shutdown the LAG, the LAG will link up/down for several times

[shuaishang]

SONiC + libteam
(all SONiC/Debian/libteam version has this issue)

Topo:

• The LAG/PortChannel has one or more members
• Create multiple subport on this LAG/PortChannel

Problem:

• shutdown the LAG, then no shutdown it: "ip link set dev PortChannel1 down/up"
• run "ip monitor" on Linux:
  when no shutdown the LAG, the LAG will link up/down for several times, depends on how many subports
• the link flapping will affect FRR and we expected only one time down/up

Why:

• when no shutdown the LAG, the linux will trigger: admin status change for LAG and all subports
  The following code "lacp_event_watch_admin_state_changed" will be called wrongly for serveral times (depends on how many subports):
  https://github.com/jpirko/libteam/blob/8b843e93cee1dab61fb79b01791201cdad45e1d1/teamd/teamd_runner_lacp.c#L1384C12-L1384C48