[FFe] Upgrading from 4.1.1 to 4.1-ESV-R4 (Extended Support Version)

We discussed a bit in #ubuntu-devel earlier last week about why we're sticking with isc-dhcp 4.1 instead of going to 4.2.
The main reason is that 4.1 is a long term supported release and so matches our goal with the LTS.

Then on Friday, I noticed that we don't actually ship that Extended Support Version but instead a pretty old ISC DHCP 4.1.1 from June 2010 with some backported patches.

So I think it'd be in our best interest to upgrade our isc-dhcp to 4.1-ESV-R4 released in December 2011 and that's the current long term support release of isc-dhcp.

The full changelog can be found at: https://deepthought.isc.org/article/AA-00566
Look for entries between 4.1.1 and 4.1-ESV-R4

As far as I can see, they are all bugfixes but considering the very large number of them, I think it's safer to ask for a proper Feature Freeze Exception anyway :)

I have a test package built in my PPA: https://launchpad.net/~stgraber/+archive/experimental/+packages

If the exception is approved, I'll start doing tests on these packages, including running the full IPv6/IPv4 test suite as well as running on all my machines here covering the DHCP server/DHCPv6 server/DHCP relay/DHCPv6 relay/DHCP client/DHCPv6 client use cases and send a call for testing to ubuntu-devel, waiting a few days for bug reports before pushing to the archive.