Refactoring the debian:8.2 images to be based on debian:jessie

[MichaelSimons]

The debian:8.2 images are currently broken for two reasons. Debian 8.2 is EOL and package feed configuration it comes with was archived to a different location. This means you can't use apt-get. To resolve this, a decision was made to refactor the 8.2 images to be based on debian:jessie.

Fixes #107

[MattGal]

Looks like it works, but should the tag not still mention that Jessie is a flavor of 8?

[MichaelSimons]

IDK, In the Docker ecosystem debian:jessie is more prevalent. If you prefer debian:8, I can go along with that usage here.

[MattGal]

nah, I trust you know the community, I am probably the problem.

[MichaelSimons]

@dotnet-bot test opensuse please

[mthalman]

Is there a reason for not updating it to stretch? Jessie will reach EOL next year and we'll be in the same boat.

[MichaelSimons]

@mthalman - I think that is the long term solution. I will log a bug for this. The short term, lower-risk fix is what I am proposing here.

[MichaelSimons]

Logged #110 to track adding stretch images.

[MichaelSimons]

The following images were produced as a result of merging this PR:

mcr.microsoft.com/dotnet-buildtools/prereqs:debian-jessie-coredeps-58e4974-20190328133153
mcr.microsoft.com/dotnet-buildtools/prereqs:debian-jessie-58e4974-20190328133153
mcr.microsoft.com/dotnet-buildtools/prereqs:debian-jessie-debpkg-58e4974-20190328133153
mcr.microsoft.com/dotnet-buildtools/prereqs:debian-jessie-corert-58e4974-20190328133153