Description
When management vrf is deleted dhcp_relay docker results in getting kernel message "unregister_netdevice waiting for mgmt to become free" continuously; it never stops.
When dhcp_relay docker is stopped, this error message goes away.

Steps to reproduce the issue:

1. Configure dhcp relay by having atleast one downstream interface and one upstream interface and ensure that process "dhcrelay" is running inside the dhcp_relay docker.
2. Execute "config vrf add mgmt" followed by "config vrf del mgmt"

Describe the results you expected:
It should not be printing any kernel message. The netdevice "mgmt" should get deleted from kernel automatically without this error.

Additional information you deem important :
While analyzing this error message, we stopped one docker after other to find that dhcp_relay is the one that results in this problem. Even though kernel is continuously printing this error message, control to the console is received after some time. On the prompt, when we execute "docker stop dhcp_relay" the kernel messages stop.
A workaround to this issue is to stop the dhcp_relay docker before creating management vrf and start it after management vrf is created. And, repeat the same while deleting the management vrf.

Output of show version:
Any recent master image (ex:15thNov2019 master image).