Full backport SRU for unattended-upgrades

[Balint Reczey]

Dear Release Team,

I would like to propose a one-off full backport of unattended-upgrades
1.1ubuntu1 to Xenial and possibly Trusty releases because selectively
backporting fixes for crashes and for issues that made u-u unreliable
would be more risky thanks to the huge number of fixes and the
inter-dependencies between them.

I prepared the backport in ppa:rbalint/scratch and also ran
autopkgtests on it [1] in addition to testing it manually in VMs.

I'm not fully satisfied with the 1.1ubuntu1 version looking at the
collected errors [2], but the fixes of those errors should be applied
on top of the 1.1ubuntu1 release possibly before letting the
backported u-u package to migrate to xenial-updates from
xenial-proposed.

With the full backport I also propose keeping it in proposed longer
than the minimum of 7 days.

Cheers,
Balint

[1] https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-xenial-rbalint-scratch/xenial/amd64/u/unattended-upgrades/20180510_130228_39002@/log.gz
[2] https://errors.ubuntu.com/?package=unattended-upgrades&period=year&version=1.1ubuntu1