[docker-dhcprelay]: Update to Bullseye

[saiarcot895]

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

Why I did it

How I did it

1. Change the dhcprelay Dockerfile to be based on docker-config-engine-bullseye instead of docker-config-engine-buster.
2. To fix some compile errors in isc-dhcp (for dhcprelay), update it to the version that's used in Bullseye. However, this version isn't in the git repository that Debian uses for packaging, since it was a NMU (non-maintainer upload). Therefore, the code to get the source code has to be changed.
3. Clean up and update the debian packaging files to automatically read and record runtime dependencies and make the build-time dependencies more accurate.
4. Modify the Bullseye slave container to just get the default Boost version's headers, instead of explicitly specifying it there.

How to verify it

Ran dhcp_relay/test_dhcpv6_relay.py and dhcp_relay/test_dhcp_relay.py and verified that they passed.

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

• 201811
• 201911
• 202006
• 202012
• 202106

Description for the changelog

Update the dhcprelay container to Bullseye, and update isc-dhcp as well

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