Code review comment for ~chad.smith/ubuntu/+source/pollinate:ubuntu/trusty-devel

I always kind of struggle for what a SRU changelog
should look like. If someone is using trusty and is reading changelogs
then they're interested in changes that they see. So the
'include img/build_name/server in user-agent' is not speficially new
as it is covered by 'Add cloud image build info'.

The same is true of 'fix bug on xen....' that never existed in trusty.
Obviously writing such a changelog means different changelogs for
each release we're doing an SRU to, and is generally more complex for
you. But does seem to me at least to provide more value to the user.

An example of a trusty and xenial changelog might be.
 * New upstream release (LP: #1761240):
   - Add hypervisor to useragent string
   - Add cloud image build info and data in /etc/pollinate/add-user-agent
     to useragent string.
   - Add '--print-user-agent' flag.
   - Speedups when collecting information for user-agent.
   - Get logger version via logger -V rather than dpkg query.
   - Perform safe read of /proc/uptime

Artful would be the same except for the 'Perform safe read..'
and bionic would have:
  - Use systemd-detect-virt if available.
  - Fix bug on xen when not booted with systemd.
  - Include img/build_name/server in user-agent.