docker-dhcp-relay: Fix waiting for interfaces to get set up

[saiarcot895]

Fix the check used to wait for interfaces to come up. The group name in
the supervisor config files has changed from isc-dhcp-relay to
dhcp-relay.

Also, in the wait script, wait 10 additional seconds after the vlans,
port channels, and any interfaces are up. This is because dhcrelay
listens on all interfaces (in addition to port channels and vlans), and
to ensure that it stays in a clean state during runtime, wait some extra
time to make sure that those interfaces are created as well.

Signed-off-by: Saikrishna Arcot [email protected]

Why I did it

How I did it

How to verify it

In the output of sudo ss -nlp, for dhcrelay and dhcp6relay, verify that all of the sockets that are bound to an interface have a valid interface name, and not some interface index number (e.g. if512, if4294967295, ...).

Example of sockets bound to interfaces that no longer exist:

udp                UNCONN              0                    0                                                                                    0.0.0.0%if1689:67                                                0.0.0.0:*                      users:(("dhcrelay",pid=155973,fd=13))
udp                UNCONN              0                    0                                                                                    0.0.0.0%if1690:67                                                0.0.0.0:*                      users:(("dhcrelay",pid=155973,fd=12))
udp                UNCONN              0                    0                                                                                    0.0.0.0%if1691:67                                                0.0.0.0:*                      users:(("dhcrelay",pid=155973,fd=11))
udp                UNCONN              0                    0                                                                                    0.0.0.0%if1692:67                                                0.0.0.0:*                      users:(("dhcrelay",pid=155973,fd=10))
udp                UNCONN              0                    0                                                                                    0.0.0.0%if1693:67                                                0.0.0.0:*                      users:(("dhcrelay",pid=155973,fd=9))
udp                UNCONN              0                    0                                                                                    0.0.0.0%if1694:67                                                0.0.0.0:*                      users:(("dhcrelay",pid=155973,fd=8))
udp                UNCONN              0                    0                                                                                    0.0.0.0%if1695:67                                                0.0.0.0:*                      users:(("dhcrelay",pid=155973,fd=7))

Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006
• 202012
• 202106

Description for the changelog

A picture of a cute animal (not mandatory but encouraged)